#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i = 0; i < (n);i++)
#define sz(x) int(x.size())
typedef long long ll;
typedef pair<int,int> P;

vector<bool> is_prime;
vector<int> sieve(int n){
    vector<int> prime;
    is_prime.resize(n+1,true);
    is_prime[0] = is_prime[1] = false;
    for(int i = 2 ; i <= n ; i++){
        if(is_prime[i]){
            prime.push_back(i);
            for(int j = 2*i; j <= n; j += i){
                is_prime[j] = false;
            }
        }
    }
    return prime;
}

int main(){
  int n;
  cin >> n;
  auto prime_table = sieve(n);
  if (n == 1) {
    cout << 0 << endl;
    return 0;
  }
  int res = 1;
  for (int i = 1; i < sz(prime_table); i++) {
    int r = prime_table[i] + 2;
    int sqr = sqrt(r);
    if (r == sqr*sqr && is_prime[sqr]) res += 2;
  }
  cout << res << endl;
  return 0;
}