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