#include <iostream>
#include <fstream>
#include <vector>
#include <algorithm>
#include <cstring>
#include <unordered_map>
#include <stack>
//#define CONSOLE /// daca ai in consola
#define int long long
using namespace std;
 
ifstream fin("ciur.in");
ofstream fout("ciur.out");
 
#ifdef CONSOLE
    #define fin cin 
    #define fout cout 
#endif
stack<bool> S;
const int MAXNR=2000000;
bool ciur[MAXNR+5];
void eratostene(){
    ciur[0]=ciur[1]=1;
    for(int i=2;i*i<=MAXNR;i++) if(!ciur[i]) for(int j=i*i;j<=MAXNR;j+=i)
    ciur[j]=true;
}
signed main() { 
    int n,cnt=0;
    fin>>n;
    eratostene();
    for(int i=1;i<=n;i++) if(!ciur[i]) cnt++;
    fout<<cnt;
    return 0;
}