import java.util.Scanner;

class Book {
    public int price;
    public int point;

    public Book(int price, int point) {
        this.price = price;
        this.point = point;
    }
}

public class Main {

    public static void main(String[] args) {

        Scanner scanner = new Scanner(System.in);
        int cases = scanner.nextInt(); 

        while( cases-- > 0 ) {
            // Do Something
            int N = scanner.nextInt();  // The number of books
            int M = scanner.nextInt();  // The number of stores

            Book books[][] = new Book[N][M];
            for(int i=0; i<N; i++) {
                for(int j=0; j<M; j++) {
                    int price = scanner.nextInt();
                    int point = scanner.nextInt();
                    books[i][j] = new Book(price, point);
                }
            }


            int min = Integer.MAX_VALUE;
            for(int i=0; i<M; i++) {
                int total_price = 0;
                int total_point = 0;
                int min_point = Integer.MAX_VALUE;

                for(int j=0; j<N; j++) {
                    total_price += books[j][i].price;
                    total_point += books[j][i].point;

                    if(min_point > books[j][i].point) min_point = books[j][i].point; 
                }

                total_point -= min_point;

                if(min > (total_price - total_point) ) min = (total_price - total_point);
            }

            System.out.println(min);
        }

    }

}