/*
TASK:minjumps
LANG:C++
*/
#include <iostream>
using namespace std;
int main()
{
const int F=-1;    
int a,b,n;
cin>>a>>b>>n;
if(a%2==0&&b%2==0&&n%2==1)
{
 cout<<F<<endl;
 return 0;
}
int i=1,j=0;
while(true)
{
 while(j<=i)
 {
  //cout<<i<<" "<<j<<endl;
  if((i*a+j*b==n)||(i*a-j*b==n)||(-i*a+j*b==n)||(-i*a-j*b==n) || (j*a+i*b==n)||(j*a-i*b==n)||(-j*a+i*b==n)||(-j*a-i*b==n))
  {
                cout<<i+j<<endl;
                return 0;
  }
  j++;
 }
  i++;
  j=0;
}


}
