#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define all(A) A.begin(),A.end()
using vll = vector<ll>;
#define rep(i, n) for (long long i = 0; i < (long long)(n); i++)
using Graph = vector<vector<ll>>;
ll mod=1e9+7;
ll sqrtz(ll N) {
    ll L = 0;
    ll R = sqrt(N)+10000;
    while (abs(R - L) > 1) {
        ll mid = (R +L) / 2;
        if (mid * mid <= N)L = mid;
        else R = mid;
    }
    return L;
    
}
int main() {
   ll N;
   cin>>N;
   vector<bool> P(1e6,true);
   P[0]=P[1]=false;
   ll an=-(N>=2);
   for(ll i=2;i<=N;i++){
     if(P[i]){
       ll j=sqrtz(i+2);
       if(j*j==i+2&&P[j])an+=2;
       for(ll m=i*2;m<=1e6-1;m+=i){
         P[m]=false;
       }
     }
   }
   cout<<an<<endl;
    

}