#include <iostream>
#include <cstring>
#include <vector>
#include <algorithm>
#include <cmath>
#include <string>
#include <set>
#include <utility>
#include <cstdlib>
#include <queue>
#include <stack>
#include <iomanip>
#include <cstdio>
#include <map>
#include <list>

using namespace std;

typedef long long Int;
typedef pair<Int,Int> P;

#define rep(i,x) for(Int i = 0; i < (Int)(x); i++)
#define rrep(i,x) for(Int i = ((Int)(x) - 1); i >= 0; i--)
#define _upgrade ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
#define all(x) (x).begin(), (x).end()
#define UNIQUE(v) v.erase( unique(v.begin(), v.end()), v.end() );
#define pb push_back
#define MX 100010


template<class T1, class T2> void chmin(T1 &a, T2 b){if(a>b)a=b;}
template<class T1, class T2> void chmax(T1 &a, T2 b){if(a<b)a=b;}

//ll gcd(ll a, ll b){return b?gcd(b,a%b):a;}
//ll lcm(ll x, ll y) {return x / gcd(x, y) * y;}

Int dx[4] = {1,0,-1,0};
Int dy[4] = {0,1,0,-1};
const Int INF = 1001002003004005006ll;
const Int mod = 1e9 + 7;
const double PI = 3.14159265358979323846;


// ****************************************CODE***************************************//







class eratosthenes{
        public:
                vector<int> prime_n;
                bool prime[500001];

                eratosthenes(){
                        fill(prime,prime+500001,true); //素数
                        prime[0] = prime[1] = false;
                        for(int i = 2; i < 500001; i++){
                                if(prime[i] == true){
                                        prime_n.push_back(i);
                                        for(int j = 2; i * j < 500001; j++){
                                                prime[i*j] = false;
                                        }
                                }
                        }
                }
};

int main(){
        eratosthenes p;
        int n;
        cin >> n;
        int ans = 1;
        if(n == 1){
                cout << 0 << endl;
                return 0;
        }
        for(int i = 1; i < p.prime_n.size() && p.prime_n[i] <= n; i++){
                int r = 2 + p.prime_n[i];
                int r_ = floor(sqrt(r));
                if(r == r_*r_ && p.prime[r_]){
                        ans += 2;
                }
        }
        cout << ans << endl;
        return 0;
}