def check(i,j):
    if (i+j)%2==0:return'#'
    return'.'

while True:
    H,W=map(int,input().split())
    if H==0 and W==0:
        break
    for i in range(H):
        for j in range(W):
            print(check(i,j),end='')
        print()
    print()
