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