x=1
y=1
list=[]
while x>0:
    if x ==0 and y == 0:
        break
    x,y = map(int,input().split())
    list.append([x,y])

L=""
for i in list:
    for h in range(i[0]):
        for w in range(i[1]):
            if (h + w)%2==0 :
                L += "#"
            else:
                L += "."
        print (L)
        L = ""
    print ()