#include <iostream>
#include <string>
#include <stack>
#include <math.h>
#include <algorithm>
#include <cstdlib>
#include <ctime>
#include <vector>

using namespace std;






int main()
{
	int n[30];
	int count;
	bool prime[1000000];
	for (int i = 0; i < 30; i++) {
		cin >> n[i];
		count = 0;
		
		for (int i = 0; i <= n[i]; i++) {
			prime[i] = true;
		}
		prime[0] = prime[1] = false;
		for (int j = 2; j <= n[i]; j++) {
			if (prime[j]) {
				for (int k = 2 * j; k <= n[i]; k += j) {
					prime[k] = false;
				}
			}
		}

		for (int j = 1; j <= n[i]; j++) {
			if (prime[j]) count++;
		}
		cout << count << endl;


	}
	

}