a, b = map(int,input().split())
cnt = 1
while a != 0:
    if cnt//2 = 1:
        if b//2 = 0:
            print('#.'*(b//2))
        else:
            print('#.'(b//2)+'#')
    else:
        if b//2 = 0:
            print('.#'*(b//2))
        else:
            print('.#'(b//2)+'.')
    print()
    a, b = map(int,input().split())
