from itertools import chain
def solution(board) :
    height = len(board)
    width = len(board[0])

    for h in range(1, height) :
        for w in range(1, width) :
            if board[h][w] != 0:
                board[h][w] += min(board[h-1][w], board[h][w-1], board[h-1][w-1])
    return max(chain(*board))**2