import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        
        //入力
        int x = Integer.parseInt(sc.next());
        int y = Integer.parseInt(sc.next());
        int z = Integer.parseInt(sc.next());
        
        //処理
        z -= Math.abs(x - y);
        int ans = Math.max(x, y) + z / 2;
        
        //出力
        System.out.println(ans);
    }
}