while 1:
        h,w=map(int,input().split())
        if h==w==0:
                break
        p=[['#'for i in range(w)] for j in range(h)]
        for i in range(w):
                for j in range(h):
                        if (i+j)%2=1:
                                p[i][j]='.'
                        else:
                                p[i][j]='#'
        print(p)

