/*
TASK:minjumps
LANG:C++
*/
#include <iostream>
using namespace std;

int min=1000000,a,b,n,k=0;

int main()
{
    cin >> a >> b >> n;
    if (n<0) n-=2*n;
    if (a%2==0 && b%2==0 && n%2!=0){ cout << "-1\n"; return 0;}
    if (a<b){k=a;a=b;b=k;}
    k=0;
    while(1)
    {
            if (n==0) break;
            if (n%a==0 && n>0){k+=n/a; break;}
            else if (n%a==0 && n<0){n-=2*n; k+=n/a; break;}
            else if (n%b==0 && n>0){k+=n/b; break;}
            else if (n%b==0 && n<0){n-=2*n; k+=n/b; break;}
            else if (n<-10000){ cout << "-1\n"; return 0;}
            n-=a;
            k++;
    }
    cout << k << endl;
            
return 0;
}
