The input is a natural number n — the number of rows and columns in the square matrix. Next, the elements of the matrix are entered line by line with a space. Output the maximum element excluding the area above the main diagonal.

def max_el_matrix(n):
  matrix = []
  for i in range(n):
    matrix.append(list(map(int, input().split())))
  max_el = -100
  for i in range(n):
    for j in range(n):
      if i < j:
        if matrix[i][j] > max_el:
          max_el = matrix[i][j]
  return max_el
    
max_el_matrix(4)