#include<iostream>
#include<string>
#include<string.h>
#include<algorithm>
#include<stdio.h>
#include<cmath>
#include<vector>
#include<utility>
#include<stack>
#include<queue>
#include<list>
#include<bitset>

#define FOR(i, a, b) for(int i=(a);i<=(b);i++)
#define RFOR(i, a, b) for(int i=(a);i>=(b);i--)
#define MOD 1000000007
#define INF 1000000000

using namespace std;

int main(void) {
	int n;
	int count = 1;
	cin >> n;
	if (n == 1) {
		cout << 0 << endl;
	}
	else if (n == 2) {
		cout << 1 << endl;
	}
	else {
		for (int t = 3; t <= n - 1; t += 2) {
			FOR(i, 1, t - 1) {
				if (t%i == 0) {
					break;
				}
				if (i == t - 1) {
					count++;
					break;
				}
			}
		}
		cout << count << endl;
	}
	
	return 0;
}
