/* -*- coding: utf-8 -*-
 *
 * 810.cc:  No.810 割った余りの個数 - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

/* typedef */

/* global variables */

/* subroutines */

/* main */

int main() {
  int l, r, m;
  scanf("%d%d%d", &l, &r, &m);

  int ld = l / m, rd = r / m;
  int lm = l % m, rm = r % m;
  int ans;

  if (ld == rd)
    ans = rm + 1 - lm;
  else if (ld + 1 == rd)
    ans = (lm > rm) ? m - lm + rm + 1 : m;
  else
    ans = m;

  printf("%d\n", ans);
  return 0;
}