import java.util.Scanner;
public class ArrayTry {
static Scanner scn = new Scanner(System.in);
public static void main(String[] args) {
int n = scn.nextInt();
for (int c = 1; c <= n; c++) {
int a = scn.nextInt();
int b = scn.nextInt();
int[] array = new int[b - a + 1];
for (int i = 0; i < array.length; i++) {
array[i] = a;
a++;
}
Display(array);
}
}
public static void Display(int[] arr) {
int s = 0;
for (int r = 0; r < arr.length; r++) {
int i = 2;
while (i <= arr[r] - 1) {
if (arr[r] % i == 0)
break;
i = i + 1;
}
if (i == arr[r])
s += 1;
}
System.out.println(s);
}
}