package com.ad;

import java.util.*;

import java.io.FileInputStream;

public class Prom_11 {

/**

* @param args

* 심해 탐사 - 기출

*/

static int N, M, W, Answer;

static int[][] S;

public static void main(String[] args)throws Exception {

// TODO Auto-generated method stub

System.setIn(new FileInputStream("src/data/prom11"));

Scanner sc = new Scanner(System.in);

int T = sc.nextInt();

for(int test_case = 1; test_case <= T; test_case++){

/////////////////////////////////////////////////////////

N = sc.nextInt();

S = new int[10000][2];

int[] sort = new int [N];

for (int i = 0; i < N; i++) {

S[i][0] = sc.nextInt();

S[i][1] = sc.nextInt();

sort[i] = S[i][1]*10000+S[i][0];

sort[i] = S[i][1]*10000+S[i][0];

//System.out.println(sort[i]);

}

Arrays.sort(sort);

for (int i = 0; i < sort.length; i++) {

System.out.println(sort[i]);

}

int sum = 0;

Answer = 0;

int max = Integer.MIN_VALUE;

for (int i = 0; i < N; i++) {

int a = sort[i]/10000;

int b = sort[i]%10000;

sum += b;

//System.out.println(sum-a);

if(sum-a > max) {

max = sum-a;

}

}

System.out.println(max);

/////////////////////////////////////////////////////////

} // end for

} // end main

}