while(True):
    H, W = map(int, input().split())
    if(H == 0 and W == 0):
        break
    else:
        fir = "#"
        sec = "."
        for i in range(H):
            for k in range(W):
                if k%2:
                    print(fir, end = "")
                else:
                    print(sec, end = "")
            print("")
            tmp = fir
            fir = sec
            sec = tmp
            print("")
