#include <bits/stdc++.h>
using namespace std;

#define int long long

int tbl[500010] = {};
vector<int> so;
set<int> st;

signed main(){
    int n;
    cin >> n;

    for(int i = 2;i <= n;i++){
        if(tbl[i] == 0){
            so.push_back(i);
            st.insert(i);
            for(int j = i*2;j <= n;j+=i){
                tbl[j] = 1;
            }
        }
    }

    int cnt = 0;

    for(int i = 0;i < so.size();i++){
        int rr = so[i]*so[i];
        if(rr > n) break;
        for(int j = 0;j < so.size();j++){
            if(rr-so[j] < 2) break;
            if(st.find(rr-so[j]) != st.end()) cnt++;
        }
    }

    cout << cnt << endl;
    return 0;
}