#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < n; ++i)
using ll = long long;
using namespace std;
const int INF = 1e9;

int main() {
    int A, B, C;
    cin >> A >> B >> C;

    if(abs(A-B)<C){
        C-= abs(A - B);
        cout << max(A, B) + C / 2;
    } else 
        cout << min(A, B) + C;

    cout << endl;

    return 0;
}