import sys
x = []
for line in sys.stdin:
    h,w = line.split()
    h,w = int(h), int(w)
    if h == 0 and w== 0: break
    tmp = (w+1)/2
    s1 = ('.#' * tmp)[:w]
    s2 = ('#.' * tmp)[:w]
    for j in range(h):
        if (j & 1)==0: s = s2
        else: s = s1
        print s
    print
    