素数筛里说丰年，听取WA声一片

#include <iostream>
#include <cmath>
using namespace std;
bool isprime (int x) {
    for (int i = 1;i <= sqrt(x);i++) {
        if (x % i == 0) return false;
    }
    return true;
}
int main(){
	int n, ans = 0;
	cin >> n; 
	for (int i = 2;i <= n;i++) {
        if (isprime(i)) ans++;
    }
    cout << ans;
	return 0;
}