def even_line(w):
    s=''
    for i in range(0,w):
        if i%2 == 0:
            s=s+'#'
        else:
            s=s+'.'
    print(s)

def odd_line(w):
    s=''
    for i in range(0,w):
        if i%2 == 0:
            s=s+'.'
        else:
            s=s+'#'

    print(s)

if __name__ == '__main__':

    h, w = map(int, input().split())

    while (h != 0) and (w != 0):
        for i in range(0,h):
            if i%2==0:
                even_line(w)
            else:
                odd_line(w)
            print()
        h, w = map(int, input().split())

