View Code of Problem 51

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