#include <bits/stdc++.h>
#define INF 990000000
//8
using namespace std;

int main() {

double x,y,z;

cin>>x>>y>>z;

int maxi=max(x,y);
int mini=min(x,y);

int sa=maxi-mini;
if(z<=sa){
mini+=z;
cout<<mini;
}else{
maxi=maxi+((z-sa)/2);
cout << maxi;
}



}