while True:
    H, W = map(int, input().split())
    if  H == 0 and W==0: break
    for i in range(H):
         if i % 2 ==0:
             print("#."*(W//2)+"#"*(W%2))
         if i % 2 ==1:
             print(".#"*(W//2)+"."*(W%2))
    print("")

