import sys


while True:
    i = 1
    h,w = map(int,raw_input().split())
    if h == 0 and w == 0:
        break
    while i <= h * w:
        if i % 2:
            sys.stdout.write("#")
        elif not i % 2:
            sys.stdout.write(".")
        if not i % w:
            sys.stdout.write("\n")
        i +=1
    sys.stdout.write("\n")