ans=[]

while True:
    H,W=map(int,input().split())
    if W==H==0:
        break
    col=''
    for i in range(W):
        if i%2==0:
            col+='#'
        else:
            col+='.'
    b=''
    for i in range(H):
        if i%2==0:
            b+=col+'\n'
        else:
            b+=col[::-1]+'\n'
    ans.append(b)


print('\n'.join(ans))
