View Code of Problem 51

#include<iostream>
#include<cstring>
using namespace std;
int main()
{
	int n;
	cin >> n;
	int num;
	int sum = 0;
	for (int i = 0; i < n; i++) {
		for (int j = 0; j < n; j++) {
			cin >> num;
			if (j <= i) {
				sum += num;
			}
		}
	}
	cout << sum;
	return 0;
}