参考答案：

#include<iostream>
#include<algorithm>
using namespace std;
int main()
{
    int t;
    cin >> t;
    while (t--)
    {
        int sum = 0;
        int n;
        cin >> n;
        for (int i = 2; i <= n; ++ i )
        {
            for (int j = 2; j <= i; ++ j )
            {
                if (i == j)
                {
                    ++sum;
                }
                if (i % j == 0)
                {
                    break;
                }
            }
        }
        cout << sum << endl;
    }
    return 0;
}

#include<iostream>
#include<algorithm>
using namespace std;
const int N = 200010;
int st[N], primes[N];
int cnt, n;
void get_primes(int n)
{
    for(int i = 2; i <= n; ++ i )
    {
        if(!st[i]) primes[cnt ++] = i;
        for(int j = 0; primes[j] <= n / i; ++ j )
        {
            st[primes[j] * i] = 1;
            if(i % primes[j] == 0 ) break;
        }
    }
}
int main()
{
    int t;
    cin >> t;
    while(t--)
    {
        cnt = 0;
        cin >> n;
        get_primes(n);
        cout << cnt << '\n';
    }
    return 0;
}