C++ :

#include <iostream>
#include <cstdio>
#include <cstdlib>
using namespace std;
int t,n,parent[11000],ans,a,b;

int root(int k)
{
	if (parent[k] == k) return k;
	else   return parent[k] = root(parent[k]);
}

void merge(int a,int b)
{
	parent[root(a)] = root(b);
}

int main()
{
	//freopen("in.txt","r",stdin);
	//freopen("out.txt","w",stdout);
	scanf("%d",&t);
	while (t--)
	{
		scanf("%d",&n);
		ans = 0;
		for (int i = 1 ; i <= 10000 ; i ++)
			parent[i] = i;
		for (int i = 1; i <= n ; i ++)
		{
			scanf("%d%d",&a,&b);
			if (root(a) != root(b)) merge(root(a),root(b));
			else ans ++;
		}
		printf("%d\n",ans);
	}
	return 0;
}