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