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
    s1 = ('.#' * ((w+1)/2))[:w]
    s2 = ('#.' * ((w+1)/2))[:w]
    for j in range(h):
        if (j & 1)==0: print s2
        else: print s1
    print
    