-- yukicoder My Practice
-- author: Leonardone @ NEETSDKASU

w = io.stdin:read("*n")
h = io.stdin:read("*n")
c = io.read():match('%S')

if c == 'B' then
	d = 'W'
else
	d = 'B'
end

s = ''

for i = 1, h do
	
	if i > 1 then
		s = s .. "\n"
	end
	
	if i % 2 == 0 then
		k = 1
	else
		k = 0
	end
	
	for j = 1, w do
		if k == 0 then
			s = s .. c
		else
			s = s .. d
		end
		k = 1 - k
	end
	
end

print(s)