#include <stdio.h>
#include <atcoder/all>
#include <bits/stdc++.h>
using namespace std;
using namespace atcoder;
using mint = modint998244353;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf32 1000000001
#define Inf64 4000000000000000001



int main(){
	
	long long a,b,c;
	cin>>a>>b>>c;
	bool f = false;
	for(long long i=1;i<=1000000;i++){
		long long t = i;
		t *= a;
		if(t-b>0)t -= b;
		if(t==c){
			cout<<i<<endl;
			f = true;
		}
	}
	if(!f)cout<<-1<<endl;
	
	return 0;
}