/*
TASK:minjumps
LANG:C++
*/
#include<iostream>
using namespace std;
int main()
{
    int minn=9999999;
    int p,q;
    int a,b,n;
    cin>>a>>b>>n;
    if(n<0) n*=-1;
    p=n/a+(n%a!=0);
    q=n/b+n%b;
    for(int i=0;i<=p;i++)
    for(int j=0;j<=q;j++)
    if((i*a+j*b)==n)
    if(i+j<minn) minn=i+j;
    
    
    for(int i=0;i<=p;i++)
    for(int j=0;j<=q;j++)
    if((i*a-j*b)==n)
    if(i+j<minn) minn=i+j;
    
    for(int i=0;i<=p;i++)
    for(int j=0;j<=q;j++)
    if((j*b-i*a)==n)
    if(i+j<minn) minn=i+j;
    
    if(minn==9999999)
    cout<<"-1"<<"\n";
    else cout<<minn<<"\n";
    //system("pause");
    return 0;
}
