/*
TASK: minjumps
LANG: C++
*/
#include <iostream>
using namespace std;
//AHhhhhhhh skakaulec !!! :) 
int a,b,n;

int modul(int j)
{
 if(j<0) return -j;
 return j;
}

int main()
{cin>>a>>b>>n;
 int min_skok=32000;
 if(!(a&1) && !(b&1) && (n&1)) {cout<<"-1"<<endl;return 0;}
 int max=10000/a;
 int k=(-1)*max;
 for(;k<=max;k++)
     {
      if( !( (n-k*a)%b ) ) {int z=n-k*a;
                            z/=b;
                            if( (modul(k)+modul(z) )<min_skok ) min_skok=modul(k)+modul(z);
                            }
      }
 if(min_skok==32000) {cout<<"-1"<<endl;return 0;}
 cout<<min_skok<<endl;
 return 0;
}
