/*
    Look at me!
    Look at me!
    Look at how large the monster inside me has become!
*/
#include<fstream>

#include<cstdio>
#include<map>
#include<typeinfo>
#include<set>
#define FIT(a,b) for(vector<int >::iterator a=b.begin();a!=b.end();a++)
#define FITP(a,b) for(vector<pair<int,int> >::iterator a=b.begin();a!=b.end();a++)
#define RIT(a,b) for(vector<int>::reverse_iterator a=b.end();a!=b.begin();++a)
#include<stack>
#define ROF(a,b,c) for(int a=b;a>=c;--a)
#include<vector>
#include<algorithm>
#define FOR(a,b,c) for(int a=b;a<=c;++a)
#define REP(a,b) for(register int a=0;a<b;++a)
#include<cstring>
#include<bitset>
#include<cmath>
#include<iomanip>
#define f cin
#define g cout
#include<queue>
#define INF 0x3f3f3f3f
#define debug cerr<<"OK";
#define pii pair<int,int>
#define mp make_pair
#define pb push_back
#define fi first
#define se second
#define ld long double
#define ll long long
#define ull unsigned long long
#define eps 1.e-7
#define BUFMAX 10100100
#define M 100005
#define N 2000100
#define mod 1000000007
#define eps 1.e-10

using namespace std;

ifstream f("ciur.in");
ofstream g("ciur.out");

int n,lp[N],sol;

int main ()
{
    f>>n;
    int la=0;
    FOR(i,2,n)
    if(!lp[i])
    {
        ++sol;
        lp[i]=la;
        int x=i;
        while(x)
        {
            for(int y=x*i;y<=n;y=y*x)
                lp[y]=x;
            x=lp[x];
        }
        la=i;
    }
    else
    {
        int x=lp[lp[i]];
        while(x)
        {
            for(int y=x*i;y<=n;y=y*x)
                lp[y]=x;
            x=lp[x];
        }
    }
    g<<sol;
    return 0;

}