#include <iostream>
using namespace std;

bool prime(int n)
{
    if (n == 1) return false;
    if (n == 2) return true;
    for (int i = 2; i <= n - 1; i++)
    {
        if (n % i == 0) return false;
    }
    return true;
}

int main()
{
	int x, y, cnt = 0;
	cin >> x >> y;
	if (x > y)
	{
	    int z = x;
	    x = y;
	    y = z;
	}
	for (int i = x; i <= y; i++)
	{
		cnt += prime(i);
	}
	cout << cnt << endl;
	return 0;
}

入门与面试，怎么ce了？连反馈信息都没有，本地正常啊