#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<ll, ll> l_l;
typedef pair<int , int> i_i;
typedef vector<ll> vel;
typedef vector<int> vei;
typedef vector<char> vec;
typedef vector<bool> veb;
typedef vector<string> ves;
typedef vector<vector<ll>> ve_vel;
typedef vector<vector<int>> ve_vei;
typedef vector<vector<char>> ve_vec;
typedef vector<vector<bool>> ve_veb;
typedef vector<vector<string>> ve_ves;
#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define rep1(i,n) for(int i=1;i<(int)(n);i++)
#define rep2(i,n) for(int i=2;i<(int)(n);i++)
#define repk(i,k,n) for(int i=k;i<(int)(n);i++)
#define fs first
#define sc second
#define pub push_back
#define pob pop_back
#define all(a) a.begin(),a.end()
#define rall(a) a.rbegin(),a.rend()
#define maxel(a) *max_element(all(a))
#define minel(a) *min_element(all(a))
#define acc accumulate
#define EPS (1e-7)
//#define INF (1e9)
#define PI (acos(-1))
#define mod (1000000007)
typedef long long int64;
const int64 INF = 1LL << 58;
#define dame { puts("-1"); return 0;}
template<class T> bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T> bool chmin(T &a, const T &b) { if (a>b) { a=b; return 1; } return 0; }

#define MAX_N 1000000
int prime[MAX_N]; //i番目の素数
bool is_prime[MAX_N+1]; //is_prime[i]==true->iはprime

//n以下の素数の数を返す
void sieve(int n) {
    int p = 0;
    rep(i,n+1) is_prime[i] = true;
    is_prime[0] = is_prime[1] = false;
    rep2(i,n+1) {
        if(is_prime[i]) {
            prime[p++] = i;
            for(int j = 2 * i; j<= n; j+= i) is_prime[j] = false;
        }
    }
    return ;
}

int main(){
	cin.tie(0);
	ios::sync_with_stdio(false);

    int N; cin >> N;
    sieve(500005);
    if(N == 1) { cout << 0 << endl; return 0; } 
    int cnt = 0;
    for(int i = 2; i <= N; i++) {
        if(!is_prime[i]) continue;
        for(int j = 2; j * j <= N + 2; j++) {
            if(!is_prime[j]) continue;
            if(2 + i == j * j) cnt++;
        }
    }
    cout << 2 * cnt - 1 << endl;
    return 0;
}