#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;

#define dbg(x) (cout<<#x<<" = "<<(x)<<'\n')
#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 // HOME

typedef long long int lld;
typedef pair<int, int> PII;
typedef pair<int, lld> PIL;
typedef pair<lld, int> PLI;
typedef pair<lld, lld> PLL;

const int INF = (1LL << 31) - 1;
const lld LINF = (1LL << 62) - 1;
const int dx[] = {1, 0, -1, 0, 1, -1, 1, -1};
const int dy[] = {0, 1, 0, -1, 1, -1, -1, 1};
const int MOD = (int)(1e9) + 7;

const int NMAX = 2000000 + 5;
const int MMAX = 100000 + 5;
const int KMAX = 100000 + 5;
const int PMAX = 100000 + 5;
const int LMAX = 100000 + 5;
const int VMAX = 100000 + 5;

int N, sol;
bool B[NMAX / 2];

int main() {
    int i, j, k, l;

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

    scanf("%d", &N);

    sol = 1;

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

    for(; k <= N; i++, k += 2)
        if(!B[i])
            sol++;

    printf("%d", sol);

    return 0;
}