import sys
num = []
for i in sys.stdin:
    H, W = i.split()
    if H == W == '0':
        break
    num.append((int(H), int(W)))

before = '.'
for cnt in range(len(num)):
    for h in range(num[cnt][0]):
        if before == '#':
            before = '.'
        elif before == '.':
            before = '#'
        for w in range(num[cnt][1]):
            if before == '.':
                print('#',end='')
                before = '#'
            elif before == '#':
                print('.',end='')
                before = '.'
        print()
    print()