/*
TASK:minjumps
LANG:C++
*/
#include<iostream>

using namespace std;

int main()
{
    int a, b, n, i, j;
    cin >> a >> b >> n;
    if(a>b) swap(b, a);
    if(a%2==0 && b%2==0 && n%2!=0)
    {
        cout << -1 << endl;
    }
    if(a%n==0 && b%n!=0) cout << n/a << endl;
    else if(b%n==0 && a%n!=0) cout << n/b << endl;
    else if(a%n==0 && b%n==0) cout << n/b << endl;
    else
        for(i=0;i<=n/a+1;i++)
            for(j=0;j<=n/b+1;j++)
            {
                if(a*i + b*j == n || a*i - b*j == n || b*i - a*j == n)
                {
                    cout << i+j << endl;
                    return 0;
                }
                else if(a*i + b*j >10000 || a*i - b*j >10000 || b*i - a*j >10000)
                {
                    cout << -1 << endl;
                    return 0;
                }
            }
         cout << -1 << endl;      
}
