/*
TASK: minjumps
LANG:C++
*/
#include<iostream.h>
#include<math.h>
long a,b,c,d,e,f,n,q;

int main()
{ cin>>a>>b>>n;
a=abs(a);
b=abs(b);
n=abs(n);
if(a%2==0 && b%2==0 && n%2!=0){cout<<-1<<endl;}
else if(a%2!=0 && b%2==0 && n%b==0){cout<<n/b<<endl;}
else if(a%2==0 && b%2!=0 && n%a==0){cout<<n/a<<endl;}


return 0;
}