The past five-plus weeks have been nothing short of a rollercoaster ride for Wall Street and investors. Between hitting an all-time closing high on Feb. 19, 2020 and the previous Monday, March 23, we witnessed the benchmark S&P 500 (SNPINDEX:^GSPC) lose 34% of its value. It marked the shortest time frame ever for the S&P 500 to push into bear market territory (16 trading sessions) and lose 30% of its value (22 trading sessions).

The market has also been exceptionally volatile on the heels of the coronavirus disease 2019 (COVID-19) spreading both globally and within the United States. Over a span of 22 trading sessions, beginning Feb. 24, 2020, the S&P 500 logged 10 of its 13-biggest single-day point declines, as well as its six-largest single-session point gains of all time.

If you're a day-trader who's tried to time this market, you've probably pulled your hair out in frustration by now. But if you're a long-term investor on the lookout for value, then the steepest correction in stock market history has provided quite the impetus to go shopping. Remember, no matter how steep or long a stock market correction is, each and every previous correction or bear market has eventually been erased by a bull-market rally.

A stopwatch which reads, Time to Buy.

Image source: Getty Images.

In other words, smart investors are going to be putting their money to work while valuations remain attractive. As we prepare to turn the page on March, here are the five top stocks that the smartest investors will be buying in April.

Amazon

Easily one of the strongest companies smart investors will be adding to their portfolios in April is e-commerce giant Amazon (NASDAQ:AMZN).

As you may have noticed, Amazon has survived this downdraft in the market substantially better than many other popular stocks. That's due, in part, to its role as the dominant e-commerce name in the United States. But it's not the company's generally low-margin retail services that should have investors flocking to Amazon. Instead, it's Amazon Web Services (AWS).

AWS is the company's cloud-services division, and it's been growing considerably quicker than its traditional retail operating segment. What's important to note about AWS is that cloud-service margins are light year's better than online retail. As a result, as AWS grows into a larger share of total sales, Amazon should witness a cash flow explosion.

According to Wall Street's consensus estimate for 2023, Amazon has the ability to generate approximately $201 in cash flow per share. Based on its current share price, that's a price to cash flow of about 9.5. By comparison, Amazon has regularly been valued at 23 to 37 its cash flow for the past decade. This demonstrates just how much upside is still left in Amazon's share price.

A person swiping a credit card through a Square reader device that's plugged into a smartphone.

Image source: Square.

Square

One of the industries that's been absolutely decimated by the coronavirus crash of 2020 is credit-service providers.

For instance, payment and point-of-sale solutions provider Square (NYSE:SQ) lost over 60% of its value in a month on fears that gross processing volume (GPV) crossing its network would plummet. Though an update last week from Square has shown GPV weakness recently, and the company was forced to modestly reduce its current-quarter guidance, Square did report 47% gross profit growth in January and February, before the you-know-what hit the fan. 

What's more, the COVID-19 crisis is shedding light on the role Cash App could play moving forward. Cash App, which allows users to send and receive money, could be a $60 billion opportunity for the company, and it's seen a record amount of new user activity recently.

Investors in Square are buying into a company expected to more than double revenue between 2020 and 2023, with earnings growth likely to triple over that time. Paying up for this type of growth absolutely makes sense.

A bank teller handing cash back to a customer.

Image source: Getty Images.

U.S. Bancorp

Although the idea of investing in big banks probably sounds less-than-palatable at the moment, smart investors will likely be looking for any reason to buy into what's likely the most efficient bank in the industry, U.S. Bancorp (NYSE:USB).

The knock against banks is that they're cyclical -- i.e., they perform poorly when recessions strike -- and they'll earn less net interest income due to the Federal Reserve pushing its federal funds target rate back to a record low. But neither is a huge concern for U.S. Bancorp, which has a history of controlling noninterest expenses and has been successful in migrating consumers over to its digital platform and mobile app. With a new generation of banking customers transacting online, the company has been able to reduce the number of U.S. Bank branches open, thereby lowering its operating expenses.

U.S. Bancorp is also much better at generating profits from its total assets than any other bank. Consistently, it has achieved the highest return on assets of any big bank, which is why it was valued at nearly twice its book value as recently as mid-February. Now, though, investors can buy into U.S. Bancorp for only 7% above book value and a little more than 7 times Wall Street's 2021 per-share profit consensus. It's been more than a decade since U.S. Bancorp has been this cheap.

A surgeon holding up a one dollar bill with surgical forceps.

Image source: Getty Images.

Intuitive Surgical

Smart investors will also be looking to buy into businesses that get better with age, like robotic-assisted surgical system developer Intuitive Surgical (NASDAQ:ISRG).

What makes Intuitive Surgical so special is the company's razor-and-blades business model. While its da Vinci surgical systems are pricey ($0.5 million to $2.5 million each), they're generally low margin considering how complex they are to build. Rather, Intuitive Surgical generates the bulk of its margin from selling accessories and instruments with each surgical procedure, and from servicing its systems. As the installed base of da Vinci systems grows worldwide, the percentage of sales being generated from these higher-margin segments should increase. In other words, Intuitive Surgical's margins should continue to get better over time.

Furthermore, the company is still just scratching the surface on what its surgical systems are capable of. Intuitive Surgical currently holds significant market share in gynecology and urology surgeries, but has plenty of opportunity to grow in thoracic, colorectal, and general soft tissue indications.

Two young adults looking at information on a laptop.

Image source: Getty Images.

Alphabet

Finally, look for smart investors to flock to Alphabet (NASDAQ:GOOG)(NASDAQ:GOOGL) in April. Alphabet being the company behind dominant search engine Google and popular content platform YouTube.

The logical concern for an ad-reliant company like Alphabet is that a sharp downturn in the economy could substantially pull back on advertiser spending and hurt its operating results. But this is unlikely to be a long-term issue, especially considering that Google holds 92% of search market share and therefore has plenty of ad-pricing power.

Alphabet is also seeing plenty of growth beyond search. Having recently published revenue data from Google Cloud and YouTube for the first time, Wall Street and investors were able to see that sales for Cloud and YouTube are up 120% and 86%, respectively, over the past two years.

But, as with Amazon, the real selling point is how inexpensive Alphabet is relative to its future cash flow. As Cloud becomes a larger component of total sales, Alphabet should see its cash flow surge higher. By 2023, Wall Street is expecting roughly $135 per share in cash flow, which is about 8 times Alphabet's current share price. For context, Alphabet has regularly been valued between 16 and 20 times its cash flow since 2013.