#include <iostream>
using namespace std;
int main(){
    int a,b,c;cin>>a>>b>>c;
    if(abs(a-b) > c){
        cout << min(a,b)+c << endl;
    }else{
        cout << max(a,b) + (c - (max(a,b)-min(a,b)))/2 << endl;
    }
}