#include<bits/stdc++.h>
using namespace std;
#define ALL(x) x.begin(),x.end()
#define rep(i,n) for(int i=0;i<(n);i++)
#define debug(v) cout<<#v<<":";for(auto x:v){cout<<x<<' ';}cout<<endl;
#define INF 1000000000
#define mod 1000000007
using ll=long long;
const ll LINF=1001002003004005006ll;
int dx[]={1,0,-1,0};
int dy[]={0,1,0,-1};
// ll gcd(ll a,ll b){return b?gcd(b,a%b):a;}
template<class T>bool chmax(T &a,const T &b){if(a<b){a=b;return true;}return false;}
template<class T>bool chmin(T &a,const T &b){if(b<a){a=b;return true;}return false;}

vector<bool> sieve(int n){
    vector<bool> ret(n+1,true);
    ret[0]=false;
    if(n>0) ret[1]=false;
    for(int i=2;i*i<=n;i++){
        if(!ret[i]) continue;
        for(int j=i*2;j<=n;j+=i) ret[j]=false;
    }
    return ret;
}


signed main(){
    cin.tie(0);
    ios::sync_with_stdio(0);
    
    int n;cin>>n;
    auto isp=sieve(n);
    vector<ll> ps;
    for(int i=2;i<=n;i++)if(isp[i])ps.push_back(i);
    set<ll> r2;
    rep(i,ps.size()) r2.insert(ps[i]*ps[i]);
    int ans=0;
    for(auto x:ps){
        if(r2.count(2+x)){
            ans+=2;
            if(x==2) ans--;
        }
    }
    cout<<ans<<endl;
    return 0;
}