'''
Given an NxN matrix of positive and negative integers, write code to find the submatrix with the largest possible sum.

Hints: 469, 511, 525, 539, 565, 581, 595, 615, 621
'''


def max_submatrix(s):
    pass

if __name__ == '__main__':
    assert max_submatrix('') ==
    assert max_submatrix('') ==
    assert max_submatrix('') ==
    assert max_submatrix('') ==
    assert max_submatrix('') ==
