#include <iostream>
using namespace std;
int main() {
int x, y , k;
cin>>x>>y>>k;
int s=abs(x)+abs(y), ost=0;
if(x==0 && y==0) ost=1;
else if (x==0 || y==0) ost=2;
if(k==1 or k==2){
cout<<s;
} else if(k%4==ost){
cout<<s+k/4+1;
} else {
cout<<-1;
}
return 0;
}
I2luY2x1ZGUgPGlvc3RyZWFtPgp1c2luZyBuYW1lc3BhY2Ugc3RkOwoKaW50IG1haW4oKSB7CiAgICBpbnQgeCwgeSAsIGs7CiAgICBjaW4+Png+Pnk+Pms7CiAgICBpbnQgcz1hYnMoeCkrYWJzKHkpLCBvc3Q9MDsKICAgIGlmKHg9PTAgJiYgeT09MCkgb3N0PTE7CiAgICBlbHNlIGlmICh4PT0wIHx8IHk9PTApIG9zdD0yOwogICAgCWlmKGs9PTEgb3Igaz09Mil7CiAgICAJCWNvdXQ8PHM7CiAgICAJfSBlbHNlIGlmKGslND09b3N0KXsKICAgIAkJY291dDw8cytrLzQrMTsKICAgIAl9IGVsc2UgewogICAgCQljb3V0PDwtMTsKICAgIAl9CiAgICByZXR1cm4gMDsKfQo=