/*
TASK:minjumps
LANG:C++
*/
#include<iostream>
using namespace std;
int main()
{
    int a,b,n,min=30000,x,y,minx,miny;
    cin>>a>>b>>n;
    for (x=-10000;x<=10000;x++)
        {
        if ((n-a*x)%b==0) {y=(n-a*x)/b;
                          if(abs(x)+abs(y)<min) {min=abs(x)+abs(y);}
                          }
        }
    if(min==30000) min=-1;
    cout<<min<<endl;
    return 0;
}
