#include <iostream>
#include <cassert>
#include <set>

using namespace std;

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

  long long A, B, C; cin >> A >> B >> C;
  set<long long> st;
  st.insert(C / A);
  st.insert((B + C) / A);
  bool ok = false;
  for (long long N: st) {
    long long x = A * N;
    if (x - B > 0) x -= B;
    if (x == C) {
      cout << N << endl;
      ok = true;
    }
  }
  if (!ok)  cout << -1 << endl;

  return 0;
}