# include <iostream>
# include <cstring>
using namespace std;

int cur = 0;
bool isp[2147483657];
int prime[2147483657];

void getprime()
{
    memset(isp, true, sizeof(isp));
    isp[0] = isp[1] = false;
    for (int i = 2; i <= 2147483647; i++)
    {
        if (isp[i])
        {
            cur++;
            prime[cur] = i;
            for (int j = 2; i * j <= 2147483647; j++)
            {
                isp[i * j] = false;
            }
        }
    }
    return;
}

int main()
{
    getprime();
    int l, r;
    cin >> l >> r;
    int ans = 0;
    for (int i = l; i <= r; i++)
    {
        if (prime[i] != 0)
            ans++;
    }
    cout << ans << endl;
    return 0;
}

居然编译失败