#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<ll, ll> P;

#define fi first
#define se second
#define repl(i,a,b) for(ll i=(ll)(a);i<(ll)(b);i++)
#define rep(i,n) repl(i,0,n)
#define all(x) (x).begin(),(x).end()
#define dbg(x) cout<<#x"="<<x<<endl
#define mmax(x,y) (x>y?x:y)
#define mmin(x,y) (x<y?x:y)
#define maxch(x,y) x=mmax(x,y)
#define minch(x,y) x=mmin(x,y)
#define uni(x) x.erase(unique(all(x)),x.end())
#define exist(x,y) (find(all(x),y)!=x.end())
#define bcnt __builtin_popcountll

#define INF 1e16
#define mod 1000000007

bool isprime[500010];

ll N;
vector<ll> ps;

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

  cin>>N;
  if(N==1){
    cout<<0<<endl;
    return 0;
  }

  repl(i,2,N+1)isprime[i]=true;
  for(ll i=2;i<=N;i++){
    if(isprime[i]){
      ps.push_back(i);
      for(ll j=2*i;j<=N;j+=i)isprime[j]=false;
    }
  }

  ll res=1;
  repl(i,1,ps.size()){
    ll r=ps[i];
    ll idx=lower_bound(all(ps),r*r-2)-ps.begin();
    if(idx<ps.size()&&ps[idx]==r*r-2){
      res+=2;
    }
  }
  cout<<res<<endl;

  return 0;
}