# -*- coding:utf-8 -*-

if __name__ == "__main__":
	w,h,c = raw_input().split()
	w = int(w)
	h = int(h)
	c = list(c)
	if c[0] == "B":
		c.append("W")
	else:
		c.append("B")
	for i in range(h):
		if w % 2 == 1:
			print ''.join(c) * (w/2) + c[0]
		else:
			print ''.join(c) * (w/2)
		c = c[::-1]