while True:
    a,b = list(map(int, input().split(" ")))
    if a == b == 0:
        break
    for i in range(1,a+1):
        if i % 2 != 0:
            if b % 2 == 0:
                print('#.' * (b / 2))
            else:
                print('#.' * ((b -1) /2) + '#')
        else:
            if b % 2 == 0:
                print('.#' * (b / 2))
            else:
                print('.#' * ((b -1) /2) + '.')
    print()