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