from __future__ import division, print_function
from sys import stdin
ROW = '#.' * 151
for line in stdin:
    h, w = (int(s) for s in line.split())
    if h == 0 and w == 0:
        break
    b = [ROW[:w], ROW[1:w+1]]
    print('\n'.join(b[y % 2] for y in range(h)), end='\n\n')