import sys
for i in sys.stdin.readlines(): 
    nums = list(map(int,i.split()))
    h = nums[0]
    w = nums[1]
    if h == 0 and w == 0:
        break
    for j in range(1,h+1):
        if h == 1 and w == 1:
            print("#")
        elif j % 2 == 1:
            x = int(w/2)
            print("#."*x)
        elif j % 2 == 0:
            x = int(w/2)
            print(".#"*x)
    print("")