/*
TASK: MINJUMPS
LANG: C++
*/
#include <iostream>
#include <math.h>
using namespace std;

int a,b,n;

int main () {
	cin >> a >> b >> n;
	int x,y,z=-1,i,h,k;
	for (i=-500000;i<=500000;i++) {
		if (!((n-a*i)%b)) {
			y=(n-a*i)/b;
			h=i;k=y;
			if ((abs(h)+abs(k)<z || z==-1)) {
				z=abs(h)+abs(k);
			}
		}
	}
	cout << z << '\n';
	return 0;
}
