/******************************************************************************
* Test solution for the Vases problem in NWERC'03 using bitmasks
* Author: Jimmy Mårdell
******************************************************************************/

#include <iostream>

using namespace std;

long long v[36];
int bitcnt[1<<18];

int countbits(long long a) { return bitcnt[a>>18]+bitcnt[a&0x3FFFF]; }

int check(int n, int cur, int sel, long long mask)
{
  if (countbits(mask)<n) return 0;
  if (sel==n) return 1;
  if (sel+36-cur<n) return 0;
  return check(n,cur+1,sel,mask) || check(n,cur+1,sel+1,mask&v[cur]);
}

int main()
{
  for(int i=0;i<(1<<18);i++) {
	int cnt=0;
	for(int j=0;j<18;j++)
	  if ((1<<j)&i) cnt++;
	bitcnt[i]=cnt;
  }

  int N;
  cin >> N;
  while (N--) {
	int m;
	cin >> m;
	for(int i=0;i<36;i++) v[i]=0;
	for(int i=0;i<m;i++) {
	  int x,y;
	  cin >> x >> y;
	  v[y-1]|=(1LL<<(x-1));
	}

	int n;
	for(n=2;n*n<=m && check(n,0,0,(1LL<<36)-1);n++);
	cout << n-1 << endl;
  }
  return 0;
}