#include <iostream>
#include <cassert>

using namespace std;

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

  int A, B, C; cin >> A >> B >> C;
  bool ok = false;
  for (int i = 1; i < 1e6; i++) {
    int x = i * A;
    if (x - B > 0) x -= B;
    if (x == C) {
      cout << i << endl;
      ok = true;
    }
  }
  if (!ok) cout << -1 << endl;
  return 0;
}