#include <bits/stdc++.h>
using namespace std;
int main() {
  int k, b, c;
  cin >> k >> b >> c;
  if (c > b) swap(b, c);
  if (c / k == 0 & b % k != 0)
    printf("%d\n", -1);
  else
    printf("%d\n", b / k + c / k);
  return 0;
}
