/* [A][M][C][B][N] / [K][R][I][P][6][8] */
#include <bits/stdc++.h>
#pragma warning(disable : 4996)
using namespace std;
// Global variables
const char sp = ' ', nl = '\n';
const int MOD = 777013; // 666013 998244353 1000000007
ifstream fin("ciur.in");
ofstream fout("ciur.out");
bool P[2000001];
void Eratostene() {
	P[1] = 1; /* 1 = compus, 0 = prim */
	for (int i = 2; i <= 2000000; i++)
		if (!P[i])
			for (int j = 2; j <= 2000000 / i; j++)
				P[i * j] = 1;
}
int main() {
	Eratostene();
	int cnt(0), n;
	fin >> n;
	for (int i = 1; i <= n; i++) if (!P[i]) cnt++;
	fout << cnt;
}