#include <iostream>
#include <vector>
#include <cmath>
#include <string>
#include <cstdio>
#include <algorithm>
#include <map>
#include <queue>
using namespace std;

#define rep(i, n) for(int (i) = (0); (i) < (n); (i++))
using ll = long long;

template <class T>
bool isPrime(T num){
    if(num <= 1) return false;
    if(num == 2) return true;
    if(num % 2 == 0) return false;

    for(int i = 3; i * i <= num; i += 2){
        if(num % i == 0){
            return false;
        }
    }

    return true;
}

template <class T>
void primeVector(vector<T>& v, T start, T end){
    for(int i = start; i <= end; ++i){
        if(isPrime(i)){
            v.push_back(i);
        }
    }
}

vector<int> v;
bool bp[500010];

int main() {
    int n;
    cin >> n;
    primeVector(v, 0, n);
    for(int i = 0; i < v.size(); ++i){
        bp[v[i]] = true;
    }

    if(n == 1){
        cout << 0 << endl;
        return 0;
    }

    int ans = 1;
    for(int i = 1; i < v.size() && v[i] <= n; ++i){
        int r = 2 + v[i];
        int rr = floor(sqrt(r));

        if(rr * rr == r && bp[rr]) {
            ans += 2;
        }
    }

    cout << ans << endl;
}