while True :
    a,b=input().split()
    h =int(a)
    w=int(b)
    if a==0 and b==0:
        break
    for i in range(h):
        if i %2==0:
            print(".#"*(w/2))
            if w==1:
                print(".")
        elif h ==1 :
            print("#")
        else:
            print("#."*((w+1)/2)-1))
            if w==1:
                print("#")

    print("")