/*
TASK: minjumps
LANG: C++
*/
#include <iostream>
#include <cmath>
using namespace std;
long long int x,y,n,br=0;
int main()
{
    cin >> x >> y >> n;
    if (n<0) n*=-1;
    int a=0;
    double b=0;
    int xx,xxx,minn=99999;
    xx=n/x;
    for (a=-n; a<=n; a++)
    {
        b=(n-a*x)/y;
        if ((n-a*x)%y==0 && abs(ceil(b))+abs(a)<minn) minn=abs(ceil(b))+abs(a); 
    }
    if (minn!=99999)
     cout << minn << '\n';
    else
     cout << "-1\n";
    return 0;
}
