import java.util.Scanner;

public class Main {

    public static boolean isPrime(int n) {
        if (n ==1 )
            return false;
        for(int i=2;i < n;i++) {
            if(n%i==0)
                return false;
        }
        return true;
    }
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);

        int cases = input.nextInt();
        int counter;
        int n;
        int m;

        for (int i = 0; i < cases; i++) {
            counter = 0;
            n = input.nextInt();
            m = input.nextInt();
            for (int j = n; j < m; j++) {
                if (isPrime(j))
                    counter++;
            }
            System.out.println(counter);
        }


    }
}