while True:
    a, b = map(int, input().split())
    if (a == 0 and b == 0):
        break
    li = [ ''.join(map(str, [ '.' if j%2==0 else '#' for j in range(i,i+b) ])) for i in range(1, a+1)]
    print('\n'.join(li)+'\n')
