import java.io.InputStream;
import java.io.PrintWriter;
import java.lang.reflect.Array;
import java.math.BigDecimal;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashSet;
import java.util.List;
import java.util.Scanner;
import java.util.Set;
import java.util.TreeSet;

import static java.util.Comparator.*;

public class Main {
    public static void main(String[] args) {
        PrintWriter out = new PrintWriter(System.out);
        Solver solver = new Solver(System.in, out);
        solver.solve();
        out.close();
    }
}
class Solver {
	Scanner sc;
	PrintWriter out;
    public Solver(InputStream in, PrintWriter out) {
    	sc = new Scanner(in);
    	this.out = out;
    }
    // ==================================================================
    public void solve() {
        int X = Integer.parseInt(sc.next());
        int Y = Integer.parseInt(sc.next());
        int Z = Integer.parseInt(sc.next());
        int sa = Math.abs(X-Y);
        if(sa == 0)			out.println(X + Z/2);
        else if(sa <= Z)	out.println(Math.max(X, Y) + (Z - sa)/2);
        else 				out.println(Math.min(X, Y) + Z);
    }
    // ==================================================================
}
class PP{
	public int key, val;
	public PP(int key, int val) {
		this.key = key;
		this.val = val;
	}
	public int getKey() {
		return key;
	}
	public int getVal() {
		return val;
	}
}