Write a program that prints the maximum element of a square matrix whose elements are entered from the keyboard, below the main diagonal. The elements of the main diagonal are also taken into account.

def max_element(matrix, index = 1):
    max_element = matrix[0][0]
    for i in range(len(matrix)):
        for j in range(i + index, len(matrix[i])):
            if max_element < matrix[i][j]:
                max_element = matrix[i][j]
    return max_element