while(True):
    x, y = map(int, input().split())
    if(x == y == 0):
        break
    for l in range(x):
        for i in range(y):
            if l % 2 ==0:
                if i % 2 == 0:
                    print ("#",end="")
                else:
                    print (".",end="")
            else:
                if i % 2 == 0:
                    print (".",end="")
                else:
                    print ("#",end="")
        print ()
