'use strict'
const main = (input) => {
  const arr = input.split(' ').map(v => parseInt(v))
  const st = arr[0]
  const ed = arr[1]
  const n = arr[2]
  console.log(parseInt(ed / n) - parseInt(st / n))
}
main(require("fs").readFileSync("/dev/stdin", "utf8"))