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