import java.util.Scanner;
public class Main{
    public static void main(String[] args) {
         Scanner scan = new Scanner(System.in);     
         String name = scan.next();     
         String sex = scan.next();     
         int age = scan.nextInt();
         Person p = new Person(name,sex,age);
         String name2 = scan.next();     
         String sex2 = scan.next();     
         int age2 = scan.nextInt();
         Person p2 = new Person(name2,sex2,age2);
         String name3 = scan.next();     
         String sex3 = scan.next();     
         int age3 = scan.nextInt();
         Person p3 = new Person(name3,sex3,age3);
         System.out.print(p3.getAvgAge()/3);
         scan.close();
    }
}
class Person
{
    private String name;
    private String sex;
    private int age;
    private static int avgAge = 0;
    public Person(String n, String s, int a)
    {
        name = n;
        sex = s;
        age = a;
        avgAge += age;
    }
    public int getAvgAge()
    {
    	return avgAge;
    }
    public void setName(String n)
    {
        name = n;
    }
    public void setSex(String s)
    {
        sex = s;
    }
    public void setAge(int a)
    {
        age = a;
    }
    public String getName() { return name;}
    public String getSex() { return sex;}
    public int getAge() { return age;}
    public void print()
    {
        System.out.print("name:"+name+"; ");
        System.out.print("sex:"+sex+"; ");
        System.out.print("age:"+age);
    }
}