#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
  #include "settings/debug.cpp"
  #define _GLIBCXX_DEBUG
#else
  #define Debug(...) void(0)
#endif
using ll = long long;
#define rep(i, n) for (int i = 0; i < (n); ++i)

int main() {
  ll a, b, c;
  cin >> a >> b >> c;
  bool exist = false;
  rep(i, 1000000) {
    ll x = a * i;
    if (x - b > 0) x -= b;
    if (x == c) {
      exist = true;
      cout << i << endl;
    }
  }
  if (!exist) cout << -1 << endl;
  return 0;
}