#include <iostream>
#include <cassert>

using namespace std;

int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);

  long long A, B, C; cin >> A >> B >> C;
  bool ok = false;
  if (C % A == 0) {
    cout << C / A << endl;
    ok = true;
  }
  if ((B + C) % A == 0) {
    cout << (B + C) / A << endl;
    ok = true;
  }
  if (!ok) cout << -1 << endl;
  return 0;
}