import sys
for line in sys.stdin:
    h, w = map(int, line.rstrip('\n').split(' '))
    if h == 0 and w == 0: break
    for y in range(h):
        row = ''
        for x in range(w):
            if (x % 2,y % 2) in ((0, 0), (1, 1)):
                row += '#'
            else:
                row += '.'
        print row
    print ''