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