'use strict'
const main = (input) => {
  const arr = input.split(' ').map(v => parseInt(v))
  const st = arr[0] / 100
  const ed = arr[1] / 100
  const n = arr[2]
  console.log((Number(ed / n) - Number(st / n)) * 100)
}
main(require("fs").readFileSync("/dev/stdin", "utf8"))