#include<algorithm>
#include<bitset>
#include<cmath>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<ctime>
#include<deque>
#include<fstream>
#include<iomanip>
#include<iostream>
#include<map>
#include<queue>
#include<set>
#include<stack>
#include<unordered_map>
#include<unordered_set>
#include<utility>
#include<vector>

using namespace std;

#ifdef HOME
const string inputFile = "input.txt";
const string outputFile = "output.txt";
#else
const string problemName = "ciur";
const string inputFile = problemName + ".in";
const string outputFile = problemName + ".out";
#endif

const int NMAX = 2000000 + 5;

int N, cnt;
bitset<NMAX> viz;

void ciur() {
    int i, j, k;

    cnt = 1;

    for(i = 1, j = 3; j * j <= N; i++, j += 2)
        if(!viz[i]) {
            cnt++;
            for(k = j * j; k <= N; k += 2 * j)
                viz[k / 2] = 1;
        }

    for(; j <= N; i++, j += 2)
        if(!viz[i])
            cnt++;
}

int main() {
#ifndef ONLINE_JUDGE
    freopen(inputFile.c_str(), "r", stdin);
    freopen(outputFile.c_str(), "w", stdout);
#endif

    scanf("%d", &N);

    ciur();

    printf("%d\n", cnt);

    return 0;
}