#include <bits/stdc++.h>
using namespace std;
constexpr static int MAXN = 1e6;
int main() {
  int k, a, b;
  cin >> k >> a >> b;
  if (a > b) swap(a, b);
  int x = a / k;
  int y = b / k;
  if (x == 0 && y == 0) {
    cout << -1 << endl;
    return 0;
  }
  if (x == 0 && b % k > 0) {
    cout << -1 << endl;
    return 0;
  }
  cout << x + y << endl;
}
