while True:
    W = input()
    H = input()
    if H == 0 and W == 0: break

    for i in range(0,H) :
        for j in range(0,W):
            if(i+j)%2 == 0:
                print("#", end='')
            else:
                print(".", end='')
        print("")
     print("") 
