#include <iostream>
#include <cmath>
using namespace std;
bool prime[500001];
void prime_found(){
  prime[0] = true;
  prime[1] = true;
  for(int i = 2; 500001 > i; i++){
    if(prime[i] == true)continue;
    for(int j = i+i; 500001 > j; j+=i){
      prime[j] = true;
    }
  }
}
int main(){
  prime_found();
  int n;cin>>n;
  int ret = 0;
  for(int i = 2; n >= i; i++){//i == r;
    //p+q==i^2
    if(prime[i])continue;
    if(i%2==0){
      for(int j = 2; i >= j && n >= j; j++){

        if((!prime[j])&&(!prime[i*i-j])){
          if(j==i*i-j)ret++;
          else ret += 2;
        };
      }
    }else{
      if((long long)i*i-2 > n)continue;
      if(!prime[i*i-2])ret+=2;
    }
  }
  cout << ret << endl;
}