#include <iostream>
#include <cmath>
using namespace std;
bool is_prime(int num) {
    if (num < 2) {
        return false;
    }

    for (int i = 2; i <= sqrt(num); i++) {
        if (num % i == 0) {
            return false;
        }
    }

    return true;
}

int main() {
    int n = 100; // n的值为100

    int prime_count = 0; // 质数个数的计数器

    for (int i = 2; i <= n; i++) {
        if (is_prime(i)) {
            prime_count++;
        }
    }

    cout << log(n) << endl;

    cout << "质数个数: " << prime_count << endl;

    double estimated_count = (n / log(n)); // 使用质数个数定理估计质数的个数

    cout << "质数个数定理估计值: " << estimated_count << endl;

    return 0;
}