#15chess
H,W=(int(i) for i in input().split())
while H!=0 or W!=0:
    S="."
    for i in range(H):
        if S[0]== "#":
            S="."
        else:
            S="#"
        for i in range(W-1):
            if S[-1]== "#":
                S+="."
            else:
                S+="#"
        print(S, end="")
    print("\n")
    H,W=(int(i) for i in input().split())