#include<bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i=0; i<(n); ++i)
using ll = long long;

int main(){
    int x,y,z; cin >> x >> y >> z;
    if(x==y){
        cout << x + z/2 << endl;
    }else{
        if(x<y) swap(x,y);
        int d = x - y;
        if(z<=d) cout << y + z << endl;
        else{
            int zz = z - d;
            cout << x + zz/2 << endl;
        }
    }
}