include <iostream>

include <vector>

include <cmath>

using namespace std;

bool check(int n){
if (n < 2) return false;
if (n == 2) return true;
if (n % 2 == 0) return false;
for(int i = 3; i <= sqrt(n); i += 2){
if (n % i == 0) return false;
}
return true;
}

int main(){
int T; cin >> T;
while(T--){
int L, R, ans = 0; cin >> L >> R;
for(int i = L; i <= R; i++){
if (check(i)){
ans++;
}
}
cout << ans << endl;
}
}