cu the thoi

#include<bits/stdc++.h>
using namespace std;
#define Fast_IO ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
#define wh while
#define fu(i,a,b,c) for(ll i=a;i<=b;i+=c)
#define fd(i,a,b,c) for(ll i=a;i>=b;i-=c)
#define in cin>>
#define out cout<<
#define ll long long
#define lo long
#define dou double
#define ld long double
#define fl float
#define sum(a,b) a+b
#define sub(a,b) a-b
#define mul(a,b) a*b
#define div(a,b) a/b
#define PI 3.14159265358979323846
#define PIn 3.14
#define en <<"\n"
#define fin(wt) freopen("wt.INP","r",stdin)
#define fout(wt) freopen("wt.OUT","w",stdout)
#define uc(a,b) __gcd(a,b)
#define bc(a,b) (a*b)/(__gcd(a,b))
#define sortup(a,n) sort(a,a+n)
#define sortdw(a,n) sort(a,a+n,greater<ll>())
#define AmuB pow(A,B)
#define elif else if
#define ndmax 1976807737
#define rt return
#define outfi(o,n) cout<<fixed<<setprecision(o)<<n
#define upper(a,i,s) upper_bound(a,a+1+i,s)
#define lower(a,i,s) lower_bound(a,a+1+i,s)
#define getl(s) getline(cin,s);
//Hello, I'm Strkss this's my acc and my code , do not copy it

int main()
{
    Fast_IO;
    bool prime[1234567]={0};
    prime[0]=1;
    prime[1]=1;
    fu(i,2,1000,1){
        if (!prime[i]){
            fu(j,i*i,1000000,i){
                prime[j]=true;
            }
        }
    }
    ll n;
    cin>>n;
    ll cnt=0;
    fu(i,5,n,1){
        if (!prime[i]&&!prime[i-2]){
            cnt++;
        }
    }
    cout<<cnt;
    return 0;
}