#include<iostream>
#include<algorithm>
#include<cmath>
using namespace std;
int main() {
  int l,r,m,a[1000000010]={0},cnt,ans=0;
  cin >> l >> r >> m;
  for(int i=l; i<=r; i++) {
      cnt=i%m;
      a[cnt]++;
      if(a[cnt]==1) {
          ans++;
      }
  }
  cout << ans << endl;
}