View Code of Problem 3493

#include <algorithm>
#include <cstring>
#include <iostream>
#include <string>
#include<cmath>
using namespace std;

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


int main()
{
    int a, b;
    while (cin >> a >> b && a != -1 && b != -1){
        int cnt = 0;
        for (int i = a; i <= b;i++){
            if(isPrime(i))
                cnt++;
        }
        cout << cnt << endl;
    }
}