Write a program that contains the basic elements of a square matrix below the main diagonal. The elements of the main diagonal are also taken into account. The input is a natural number n is the number of rows and columns in the matrix, the number of matrix elements (integers) line by line, separated by a space.

n = int(input("Please insert n: "))
matrix = [[0 for i in range(n)] for j in range(n)]

for i in range(n):
  for j in range(n):
    matrix[i][j] = int(input("Please insert matrix[{}][{}]: ".format(i, j)))
    
diagonal = 0
for i in range(n):
  for j in range(n):
    if i == j or i + j == n - 1:
      diagonal += matrix[i][j]
      
print("The sum of the diagonal is: " + str(diagonal))