import java.util.*;
import java.lang.*;
import java.io.*;

// The main method must be in a class named "Main".
import java.util.*;
class Main {
    public static int avg(int a,int b,int c){
        int avg=(a+b+c)/3;
        return avg;
    }
    public static void main(String[] args) {
        Scanner n=new Scanner(System.in);
        int a=n.nextInt();
        int b=n.nextInt();
        int c=n.nextInt(); 
        int total=avg(a,b,c);
        System.out.println(total);
    }
}