ice_cream's world is a rich country, it has many fertile lands. Today, the queen of ice_cream wants award land to diligent ACMers. So there are some watchtowers are set up, and wall between watchtowers be build, in order to partition the ice_cream’s world. But how many ACMers at most can be awarded by the queen is a big problem. One wall-surrounded land must be given to only one ACMer and no walls are crossed, if you can help the queen solve this problem, you will be get a land.

3

大意：有n个碉堡，m种关系每个关系表示两个碉堡连在一起，问一共有多少环。
父结点相等就有一个环。

 #include<cstdio>

 int n,m,fa[],i,a,b,sum;

 int find(int a)

 {

     int r=a;

     while(r != fa[r])

     {

         r=fa[r];

     }

     int i=a,j;

     while(i != r)

     {

         j=fa[i];

         fa[i]=r;

         i=j;

     }

     return r;

 }

 void f1(int x,int y)

 {

     int nx,ny;

     nx=find(x);

     ny=find(y);

     if(nx != ny)

     {

         fa[nx]=ny;

     }

     else

     {

         sum++;

     }

 }

 int main()

 {

     while(scanf("%d %d",&n,&m)!=EOF)

     {

         sum=;

         for(i =  ; i < n ; i++)

         {

             fa[i]=i;

         }

         for(i =  ; i < m ; i++)

         {

             scanf("%d %d",&a,&b);

             f1(a,b);

         }

         printf("%d\n",sum);

     }

 }