#include <bits/stdc++.h>
using namespace std;
using ll = long long;
int main() {
  long long L,R,M; cin >> L >> R >> M;
  long long x = R / M;
  long long y = L / R;
  if(x - y > 1) {
    cout << M << endl;
  }else {
    cout << R - L + 1 << endl;
  }
}