【易爆物】 LA3644

#include<iostream>
using namespace std;
#define maxn 100009
int pa[maxn];
int findset(int x)
{
    return pa[x]!=x?pa[x]=findset(pa[x]):x;
}

int main()
{
    int x,y;
    for(int i=0;i<=maxn;i++)
    pa[i]=i;
    while(scanf("%d",&x)==1)
    {
        int refusal=0;
        while(x!=-1)
        {
            scanf("%d",&y);
             x=findset(x);y=findset(y);
            if(x==y) refusal++;
            else
             pa[x]=y;
            scanf("%d",&x);
        }
        printf("%d\n",refusal);
    }
   return 0;    
}