import java.util.Arrays;
import java.util.Scanner;

public class BookStore1 {

static Scanner stdin = new Scanner(System.in);
static int N;
static int M;
static int[] res;

public static void main(String[] args) {
    // TODO Auto-generated method stub
    int numOfTest = stdin.nextInt();
    res = new int[numOfTest];

    int[][] bookList = null;
    int[][][] depBooklist = null;

    int[] minPoint = null;
    int[] minPoint_book = null;

    int count = 0;
    int count_point = 0;

    for (int t = 0; t < numOfTest; t++) {
        N = stdin.nextInt();
        M = stdin.nextInt();

        bookList = new int[N][2 * M];
        depBooklist = new int[M][N][2];


        minPoint = new int[M];
        minPoint_book = new int[M];


        for (int i = 0; i < M; i++) {
            minPoint[i] = 10001;
        }

        for (int i = 0; i < N; i++) {
            count = 0;
            count_point = 0;
            for (int j = 0; j < 2 * M; j++) {
                bookList[i][j] = stdin.nextInt();

                if (j % 2 == 0) {
                    depBooklist[count][i][0] = bookList[i][j];

                    count++;
                } else {

                    depBooklist[count_point][i][1] = bookList[i][j];

                    if (minPoint[count_point] > bookList[i][j]) {
                        minPoint[count_point] = bookList[i][j];
                        minPoint_book[count_point] = bookList[i][j - 1];
                    }
                    count_point++;
                }

            }// 삼중 for 끝
        }// 이중 for 끝


        res[t]=check(depBooklist, minPoint, minPoint_book);
    }// for 끝



      for (int i : res) { System.out.println(i); }


}

// M N 2 minpoint minPoint_book은 M만큼 생성됨
public static int check(int[][][] depBooklist, int[] minPoint, int[] minPoint_book) {

    int size = minPoint.length;
    int result;
    int[] bookCost = new int[size];
    int[] currPoint = new int[size];

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

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

            if(minPoint[i] != depBooklist[i][j][1]){

                if(bookCost[i] == 0)
                {
                    bookCost[i]=depBooklist[i][j][0]+bookCost[i];
                    currPoint[i]=depBooklist[i][j][1]+currPoint[i];
                }
                else if(depBooklist[i][j][0] >= currPoint[i]) {

                    bookCost[i]=depBooklist[i][j][0]+bookCost[i]-currPoint[i];
                    currPoint[i]=depBooklist[i][j][1];

                }
                else if(depBooklist[i][j][0] < currPoint[i]){

                    currPoint[i]=currPoint[i]-depBooklist[i][j][0]+depBooklist[i][j][1];

                }

            }
        }// 이중 for 끝

    }// for 끝

    for (int i = 0; i < M; i++) {
        if(currPoint[i]<minPoint_book[i])
            bookCost[i]=minPoint_book[i]+bookCost[i]-currPoint[i];

    }

    Arrays.sort(bookCost);
    result=bookCost[0];

    return result;

}

}