while True:
    data = map(int, raw_input().split())
    if data[0] == 0 and data[1] == 0:
        break
    else:
        for i in range(data[0]):
            if i % 2 == 0:
                for j in range(data[1]):
                    if j % 2 == 0:
                        print "#" ,
                    elif j % 2 == 1:
                        print ".",
                print
            elif i % 2 == 1:
                for j in range(data[1]):
                    if j % 2 == 0:
                        print "." ,
                    elif j % 2 == 1:
                        print "#",
                print
        print
        