2번

package JavaFestival;

import java.util.Scanner;

public class ja2 {

	public static void main(String[] args) {
	Scanner sc = new Scanner(System.in);	
	int num=0;
	int num1=1;
	for(int i=77;i>=1;i--) {
		num+=i*num1;
		num1++;
		}
	System.out.println(num);
	}
}