Write a program that prints the maximum element in the area below the main diagonal of a square matrix.

def max_under_diagonal(matrix):
    max_el = None
    for i in range(len(matrix)):
        for j in range(len(matrix[i])):
            if i + j < len(matrix) - 1:
                if max_el is None or matrix[i][j] > max_el:
                    max_el = matrix[i][j]
    return max_el

print(max_under_diagonal([[2, 3, 1], [4, 6, 5], [7, 9, 8]]))