#ifdef ONLINE_JUDGE
	#include <bits/stdc++.h>
#else
	#include <algorithm>
	#include <bitset>
	#include <cassert>
	#include <cmath>
	#include <cstdio>
	#include <cstdlib>
	#include <cstring>
	#include <iostream>
	#include <map>
	#include <set>
	#include <stack>
	#include <string>
	#include <utility>
	#include <vector>
	#include <queue>
	#include <climits>
#endif

using namespace std;

	// lambda : [] (int a, int b) -> bool { body return }
	// string r_str = R"(raw string)"

#define mp make_pair
#define mt make_tuple
#define eb emplace_back
#define pb push_back
#define LL long long
#define ULL unsigned long long
#define BASE 73
#define NMAX 10000
#define NMAX2 20001
#define MOD1 1000000007
#define ALL(V) (V).begin(), (V).end()
#define ALLR(V) (V).rbegin(), (V).rend()
#define CRLINE Duxar(__LINE__);
#define SHOWME(x) cerr << __LINE__ << ": " << #x << " = " << (x) << endl;
#define ENTER putchar('\n');

int dx4[] = {-1, 0, 1, 0};
int dy4[] = {0, 1, 0, -1};

int dx8[] = {-1, -1, 0, 1, 1, 1, 0, -1};
int dy8[] = {0, 1, 1, 1, 0, -1, -1, -1};

void Duxar(int _this_line) {
#ifndef ONLINE_JUDGE
	printf("\n . . . . . . . . . . . . . Passed line - %d\n", _this_line);
#endif
}

template <class T>
void ReadNo(T &_value) {
	T _sign = 1;
	char ch;
	_value = 0;
	while(!isdigit(ch = getchar())) {
		(ch == '-') && (_sign = -1);
	}
	do {
		_value = _value * 10 + (ch - '0');
	} while(isdigit(ch = getchar()));
	_value *= _sign;
}

int N;
vector <bool> sieve;

int main(){
	string file_input = "ciur";
#ifdef INFOARENA
	freopen((file_input + ".in").c_str(), "r", stdin);
	freopen((file_input + ".out").c_str(), "w", stdout);
#else
#ifndef ONLINE_JUDGE
	freopen("input.cpp", "r", stdin);
#endif
#endif
	
	int i, ans = 1, j;
	
	ReadNo(N);
	sieve.resize(N);
	
	for (i = 4; i <= N; i += 2) {
		sieve[i] = 1;
	}
	
	for (i = 3; (LL) i * i <= N; i += 2) {
		if (!sieve[i]) {
			for (LL j = (LL) i * i; j <= N; j += i) {
				sieve[j] = 1;
			}
		}
	}
	
	for (i = 3; i <= N; i += 2) {
		ans += (sieve[i] == 0);
	}
	
	printf("%d\n", ans);
	
	return 0;
}