#include <iostream>
#include <map>
using namespace std;

int main() {
    int L,R,M;
    cin>>L>>R>>M;
    map<int, int> mp;
    for (int i = L; i <= R; i++) {
        if (mp.find(i % M) != mp.end()) {
            break;
        }
        mp[i % M] = 1;
    }
    cout << mp.size() << endl;
    return 0;
}