/*
TASK:minjumps
LANG:C++
*/
#include <iostream>
#include <math.h>
using namespace std;
int main ()
{
    int a,b,n,i=0,br=0,z=0,br1=0;
    cin>>a>>b>>n;
    n=abs(n);
    if ((n%2!=0)&&(a%2==0)&&(b%2==0))
    {
        cout<<"-1"<<endl;
        return 0;
    }
    else if (a>b)
    {
        if (n%a==0)
        {
            cout<<n/a<<endl;
            return 0;
        }
        while (i<n)
        {
            i=i+a; 
            br++;
            br1=0;
            while (z<a)
            {
                z=z+b;
                br1++;
                if (i+z==n) 
                {
                    cout<<br+br1<<endl;
                    return 0;
                }
            }
        }
        if (i>n)
        {
            br1=0;
            while (i<n)
            {
                i=i-a;
                br1++;
                if (i==n) 
                {
                    cout<<(br+br1)<<endl;
                    return 0;
                }
            }
        }
    }
    else if (a<b)
    {
        if (n%b==0)
        {
            cout<<n/b<<endl;
            return 0;
        }
        while (i<n)
        {
            i=i+b;
            br++;
            br1=0;
            z=0;
            while (z<b)
            {
                z=z+a;
                br1++;
                if (i+z==n) 
                {
                    cout<<br+br1<<endl;
                    return 0;
                }
            }
        }
        if ((i>n)&&(i<n))
        {
            if (i<n)
            {
                i=i+b;
                br++;
            }
            br1=0;
            while (i<n)
            {
                i=i-a;
                br1++;
                if (i==n) 
                {
                    cout<<(br+br1)<<endl;
                    return 0;
                }
            }
        }
    }
    else 
    {
        if (n%a==0)
        {
            cout<<n/a<<endl;
            return 0;
        }
        else
        {
            cout<<"-1"<<endl;
            return 0;
        }
    }   
}
