Which Stephen King story is the movie "Stand by Me" based on?

"Four kids go searching for a dead body" doesn't sound like the makings of a great coming-of-age story, but "Stand by Me" proves me wrong on every rewatch. But before Rob Reiner's classic turned River Phoenix, Wil Wheaton, Corey Feldman, and Jerry O'Connell into instant stars, it was a novella by Stephen King. Which King story is the movie "Stand by Me" based on?