View Code of Problem 51

import java.util.*;
public class Main {
		public static void main(String[] args) {
			Scanner sc = new Scanner(System.in);
			int n = sc.nextInt();
			int arr[][] = new int[n][n];
			for (int i = 0; i < arr.length; i++) {
				for (int j = 0; j < arr.length; j++) {
					arr[i][j] = sc.nextInt();
				}
			}
			int sum = 0;
			for (int i = 0; i < arr.length; i++) {   
				for (int j = 0; j <= i; j++) {  
					sum += arr[i][j];	
				}
		}
			System.out.println(sum);
		}
}