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

def max_elem(mat):
    i = 0
    max_elem = -10000
    while i < len(mat):
        j = 0
        while j < len(mat[i]):
            if j > i and mat[i][j] > max_elem:
                max_elem = mat[i][j]
            j += 1
        i += 1
    return max_elem

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