# -*- coding:utf-8 -*-
while True:
    H,W = map(int, input().split())
    if H == 0 and W == 0:
        break
    for i in range(H):
        for j in range(W):
            if (i +j)%2==0 or (i+j)==0:
                print("#",end = '')
            else:
                print(".",end='')
        print()