#include <iostream>
#include<string>
#include<cmath>
#include<algorithm>
#include<cctype>
#include<queue>
#include<stack>
#include<stdio.h>
#include<vector>
#include<set>
#include<map>
#include<iomanip>
#define rep(i,n) for(int i=0;i<n;i++)
typedef int long long ll;

using namespace std;
/*int main(){
    
    ll n;
    while (cin>>n) {
        vector<ll> v;
        for(int i=0;i<n+1;i++){
            v.push_back(i);
        }
        ll b=v[v.size()-1];
        for(int i=2;i<=n;i++){
            ll j=2;
            while(i*j<=b){
                v[i*j]=0;
                j++;
            }
        }
        ll ans=0;
        for(int i=0;i<v.size();i++){
           // cout<<v[i]<<endl;
            if(v[i]!=0)ans++;
        }
        cout<<ans-1<<endl;
    }
    
    
    return 0;
}*/
int main(){
    
    ll n;
    while(cin>>n){
        ll ans=0;
        for(int i=3;i<=n;i+=2){
            int flag=0;
        for(int j=3;j<i;j+=2){
            if(i%j==0){
                flag=1;
                break;
            }
        }
            if(flag==0){
                ans++;
            }
    }
        cout<<ans+1<<endl;
        }
    
    
    
    
    
    
    return 0;
}

