a = []
while True:
    d = list(map(int,input().split()))
    if d == [0,0]:
        break
    a.append(d)

for H,W in a:
    for i in range(0,W):
        s = ''
        for j in range(0,H):
            if (i - j) % 2 == 0:
                s += '#'
            else:
                s += '.'
        print(s)
    print('')