#include <bits/stdc++.h>
long long a, b, c, cnt1, cnt2;
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  cin >> a >> b >> c;
  if (c != 0) cnt1 += c / a;
  if (b != 0) cnt2 += b / a;
  if (cnt1 == 0 && b % a != 0) {
    cout << -1;
    return 0;
  }
  if (cnt2 == 0 && c % a != 0) {
    cout << -1;
    return 0;
  }
  if (cnt1 + cnt2 == 0) {
    cout << -1;
    return 0;
  }
  cout << cnt1 + cnt2;
}
