#include <stdio.h>
#include <string>
#include <iostream>
#include <iomanip>
#include <map>
#include <algorithm>
#include <vector>
#include <math.h>
#define MOD (long long)1000000007
using namespace std;

int main(void){
    int l,r,m;
    cin >> l >> r >> m;
    int check=-1,ans=1;
    check=l%m;
    for(int i=l+1; i<=r; i++){
        if(i%m==check)break;
        ans++;
    }
    cout << ans << endl;
    return 0;
}