#define _USE_MATH_DEFINES

#include <iostream>		//cin, cout
#include <vector>		//vector
#include <algorithm>	//sort,min,max,count
#include <string>		//string,getline, to_string
#include <cstdlib>		//abs(int)
#include <utility>		//swap, pair
#include <deque>		//deque
#include <climits>		//INT_MAX
#include <bitset>		//bitset
#include <cmath>		//sqrt, ceil. M_PI, pow, sin
#include <ios>			//fixed
#include <iomanip>		//setprecision
#include <sstream>		//stringstream
#include <numeric>		//gcd, assumlate
#include <random>		//randam_device
#include <limits>		//numeric_limits
#include <time.h>       //tm

using namespace std;
constexpr int64_t D_MOD = 1000000007;

int main() {

    int A, B, C;
    cin >> A >> B >> C;

    bool flg = true;
    int n;

    for (int i = 1; i <= 200000; i++) {
        n = i * A;
        if (n - B > 0) {
            n -= B;
        }
        if (n == C) {
            cout << i << endl;
            flg = false;
        }
    }

    if (flg) {
        cout << -1 << endl;
    }

    return 0;

}