#include<bits/stdc++.h>
using namespace std;
 
#define maxPN 1000000
#define PNs  1000100
int countPN = 0, countPNs = 0;
long long PrimeNum[maxPN], temp;
bool PN[PNs];
 
bool IsPrimeNumber(long long x);
 
void PrimeN(){
    int i, j;
    PrimeNum[0] = 2;
    PN[2] = true;PrimeNum[countPN++] = 2;
    PN[3] = true;PrimeNum[countPN++] = 3;
//  PN[5] = true;PrimeNum[countPN++] = 5;
     
    for(i = 6; i  < PNs;i+=6){
        if(IsPrimeNumber(i-1)){
            PrimeNum[countPN++] = i-1;
            PN[i-1] = true;//cout<<i-1<<endl;
        }
        if(IsPrimeNumber(i+1)){
            PrimeNum[countPN++] = i+1;
            PN[i+1] = true;//cout<<i+1<<endl;
        }
        countPNs = i+1;//cout<<i-1<<" "<<PN[i-1]<<endl;
    }
}
 
bool IsPrimeNumber(long long x){
    //if(x == 2 || x == 3) return true;
    //if(x <= 4 || x%2 == 0 || x%3 == 0)   return false;
    //if(x < countPNs) return PN[x];
    for(long long i = 0; PrimeNum[i] * PrimeNum[i] <= x; i++)
        if(x%PrimeNum[i] == 0)return false;
    return true;
}
 
 
int main(){
    clock_t start, end;
    long long n = true, counta;
    start = clock();
    PrimeN();
//  cout<<PrimeNum[countPN-1]<<" "<<countPNs<<endl;
//  cout<<clock()-start<<"ms"<<endl;
     
    while(cin>>n){
        counta = 1;
         
         
        //cout<<(IsPrimeNumber(n)?"yes":"no")<<endl;
        start = clock();
        //cout<<IsPrimeNumber(n)<<endl;
        for(int i = 1; i <= n; i+=2){
            if(PN[i])counta++;
        //  cout<<i<<" "<<PN[i]<<endl;
        }
        if(n == 1) counta = 0;
        cout<<counta<<endl;
    //  cout<<clock()-start<<"ms"<<endl;
    }
    return 0;
