#!/usr/bin/env python

import sys

if __name__ == '__main__':
    while True :
        h, w = map(int, raw_input().split())
        if h == 0 and w == 0:
            break

        for i in range(h):
            for j in range(w):
                sys.stdout.write('#' if (i+j) % 2 == 0 else '.')
            print
        print


