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
    x.append([h,w])

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