#include <bits/stdc++.h>
using namespace std;
int main() {
  int k, a, b;
  cin >> k >> a >> b;
  if (a < k && b < k || (a % k != 0 && b < k) || (b % k != 0 && a < k))
    cout << -1;
  else {
    cout << a / k + b / k;
  }
}
