def line1(n):
    if n == 1:
        return("#")
    if n % 2 ==0:
        return "#." * (n/2)
    else:
        return "#." * (n/2) + "#"

def line2(n):
    if n == 1:
        return(".")
    if n % 2 ==0:
        return ".#" * (n/2)
    else:
        return ".#" * (n/2) + "."

while True:
    H, W = map(int, raw_input().split())
    if H == W == 0:
        break
    for i in xrange(H):
        if i % 2 == 0:
            print line1(W)
        else:
            print line2(W)
    print