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from sys import stdin, stdout
def parity(table):
	res = 0
	for i_row, row in enumerate(table):
		for i_col, c in enumerate(row):
			if c != ".":
				res += i_row
				res += i_col
				res %= 2
	return res

def degree(table):
	res = 0
	for row in table:
		for c, d in zip(row[:-1], row[1:]):
			if c != d:
				res += 1
	for row, next_row in zip(table[:-1], table[1:]):
		for c, d in zip(row, next_row):
			if c != d:
				res += 1
	return res

def calculate_pieces(table):
	res = 0
	for row in table:
		for c in row:
			if c != ".":
				res += 1
	return res

def total_moves(n, m):
	return 2 * n * m - n - m

def binomial(n, k):
    ''' Binomial coefficient aka the "choose" function 
        n! / (k! * (n - k)!)
    '''
    p = 1    
    for i in range(1, min(k, n - k) + 1):
        p *= n
        p //= i
        n -= 1
    return p

def edges_per_move(n, m, pieces):

	return binomial(n * m - 2, pieces - 1)

n, m = [int(x) for x in stdin.readline().split()]

start_table = []
for _ in range(n):
	start_table.append(stdin.readline().strip())

_ = stdin.readline()

end_table = []
for _ in range(n):
	end_table.append(stdin.readline().strip())

if parity(start_table) != parity(end_table):
	stdout.write("0\n")
else:
	pieces = calculate_pieces(end_table)
	res = degree(end_table)/ (total_moves(n, m) * edges_per_move(n, m, pieces))
	stdout.write(f"{res:.15f}\n")