#include <cstdio>
#include <cstring>
#include <iostream>
#include <string>
#include <cmath>
#include <bitset>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <deque>
#include <algorithm>
#include <complex>
#include <unordered_map>
#include <unordered_set>
#include <random>
#include <cassert>
#include <fstream>
#define popcount __builtin_popcount
using namespace std;
typedef long long int ll;
typedef pair<int, int> P;
const int MAX=600010;
vector<ll> prime;
bool isprime[MAX];
void sieve(){
	for(ll i=3; i<MAX; i+=2){
		isprime[i]=1;
	}
	isprime[2]=1;
	prime.push_back(2);
	for(ll i=3; i<MAX; i++){
		if(isprime[i]){
			prime.push_back(i);
			for(ll j=2*i; j<MAX; j+=i){
				isprime[j]=0;
			}
		}
	}
	return;
}
int main()
{
    int n; cin>>n;
    sieve();
    if(n==1){
        cout<<0<<endl; return 0;
    }
    if(n==2){
        cout<<1<<endl; return 0;
    }
    int sq[1000010]={};
    for(int i=1; i*i<=2*n; i++){
        sq[i*i]=i;
    }
    int ans=1;
    for(int i=1; prime[i]<=n; i++){
        int x=sq[2+prime[i]];
        if(x>0 && isprime[x]) ans+=2;
    }
    cout<<ans<<endl;
    return 0;
}