// Undone
#include <bits/stdc++.h>
#define REP(i, n) for(int i=0;i<(n);++i)
#define LL long long
using namespace std;

int main(void) {

  LL L, R, M;
  cin >> L >> R >> M;
  LL calc[M];
  for (LL i = L; i <= R; i++) {
    calc[i%M] = 1;
  }
  LL ans = 0;
  for (LL i = 0; i < M; i++) ans += calc[i];
  cout << ans << endl;
}