C++ :

#include <iostream>
using namespace std;
int main() {
    int a, b;
    cin >> a >> b;
    int c = 0;
    for (int n = a; n <= b; n++) {
        int is = 1; 
        for (int i = 2; i < n; i++) {
            if (n % i == 0) {
                is = 0;
                break;
            }
        }
        if (is==1) {
            c++;
        }
    }
    cout << c ;
    return 0;
}