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 matrix():
  n = int(input())
  a = []
  for i in range(n):
    a.append([int(s) for s in input().split()])
  res = -100
  for i in range(n):
    for j in range(n):
      if i > j and a[i][j] > res:
        res = a[i][j]
  print(res)
  
matrix()