func maximalSquare(matrix [][]byte) int {
	n := len(matrix)
	if n == 0 {
		return 0
	}
	m := len(matrix[0])
	if m == 0 {
		return 0
	}
	hei := make([][]int, n) // Init the accumulative height matrix
	hei[0] = make([]int, m)
	for i := range matrix[0] {
		hei[0][i] = int(matrix[0][i]-'0')
	}
	for i := 1; i < m; i++ {
		hei[i] = make([]int, m)
		for j := range matrix[i] {
			if matrix[i][j] == '0' {
				hei[i][j] = 0
			} else {
				hei[i][j] = hei[i-1][j] + 1
			}
		}
	}
	return 0
}