>   说两点，首先，顶点序号可能不连续，第二，注意每组数据后要输出一个换行，且前面还要输出两个空格。
> 
> 数据如下
> 1 2
> 5 4
> 3 1
> 3 2
> 3 4
> 3 5
> 0
> 
> 1 2
> 2 3
> 3 4
> 4 5
> 5 1
> 0
> 
> 1 2
> 2 3
> 3 4
> 4 6
> 6 3
> 2 5
> 5 1
> 0
> 
> 1 2
> 0
> 
> 1000 999
> 999 998
> 998 997
> 997 1000
> 0
> 
> 1 2
> 2 3
> 0
> 
> 1 2
> 1 3
> 1 4
> 1 5
> 0
> 
> 1 2
> 1 3
> 1 4
> 2 3
> 2 5
> 2 6
> 3 7
> 3 8
> 7 8
> 0
> 
> 1 2
> 1 3
> 1 4
> 1 5
> 2 3
> 2 4
> 2 5
> 3 4
> 3 5
> 4 5
> 0
> 
> 0
> 
> Network #1
>   SPF node 3 leaves 2 subnets
> 
> Network #2
>   No SPF nodes
> 
> Network #3
>   SPF node 2 leaves 2 subnets
>   SPF node 3 leaves 2 subnets
> 
> Network #4
>   No SPF nodes
> 
> Network #5
>   No SPF nodes
> 
> Network #6
>   SPF node 2 leaves 2 subnets
> 
> Network #7
>   SPF node 1 leaves 4 subnets
> 
> Network #8
>   SPF node 1 leaves 2 subnets
>   SPF node 2 leaves 3 subnets
>   SPF node 3 leaves 2 subnets
> 
> Network #9
>   No SPF nodes