/*
TASK: minjumps
LANG: C++
*/
#include<iostream>
using namespace std;
int a,b,n,i,j,back=1,pog,pom,ka;
int skok()
{
    if(j>n) if( (j-n)%pom==0) {
                               back+=(j-n)/pom;
                               return 1;
                              }
            else {
                  j+=pog; back++; return skok(); 
                 }
    else {if((n-j)%pom==0) { 
                              back+=(n-j)/pom;
                              return 1;
                           }
          else {j+=pog; back++;return skok();}
         } 
} 
int main ()
{
    cin>>a;
    cin>>b;
    cin>>ka;
    if(ka<0) n=-ka;
    else n=ka;
    if(a>b) {pog=a;pom=b;}
    else {pog=b;pom=a;}
    j=pog;
    if(a%2==0&&b%2==0&&n%2!=0) cout<<"-1";
    else if(j==n) cout<<"2";
         else if(a==n||b==n) cout<<"1";
              else {
    if(pom==1) cout<<n/pog+n-pog*(n/pog);
    else if(n%pog==0) cout<<(n/pog);
         else if(n%pom==0) cout<<n/pom;
              else {
                    skok ();
                    cout<<back;
                   }
                   }
    cout<<endl;
    return 0;
}    
