import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int x = Integer.parseInt(sc.next());
        int y = Integer.parseInt(sc.next());
        int z = Integer.parseInt(sc.next());

        int res = 0;
        if(x < y) {
            res += x;
            res += (y - x + z) / 2;
        } else {
            res += y;
            res += (x - y + z) / 2;
        }

        System.out.println(res);
    }
}