#include <bits/stdc++.h>

using namespace std;

int main(){
    int x,y,z;
    cin >> x >> y >> z;
    if(abs(x-y)>=z){
        cout << min(x,y)+z << endl;
    }
    else{
        cout << max(x,y)+(z-abs(x-y))/2 << endl;
    }
}