#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 << endl;
    return 0;
  }
  cout << a / k + b / k << endl;
  return 0;
}
