while True:
    h,w = map(int,input().split())
    if h == 0 and w == 0:
        break
    sym1 = "#"
    sym2 = "."
    for i in range(h):
        if i%2 = 1:
		    sym1 = "#"
		    sym2 = "."
        else:
		    sym1 = "."
		    sym2 = "#"

        for j in range(w):
	        if j%2 == 1:
	            print(sym1,end="")
	        else:
	            print(sym2,end="")
	    print("")
    
    print("")