#include <bits/stdc++.h>
int main() {
  int a, b, c, aa, bb, n;
  scanf("%d %d %d", &a, &b, &c);
  aa = a - a % c;
  bb = b - b % c;
  n = (bb - aa) / c + (a % c == 0) ? 1 : 0;
  printf("%d\n", n);
  return 0;
};
