import java.io.*;
import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        int n = sc.nextInt();
        int size = (int)(Math.sqrt(n)) + 1;
        ArrayList<Integer> listPrimes = new ArrayList<>();
        boolean[] isNotPrime = new boolean[size];
        for (int i = 2; i < size; i++) {
            if (!isNotPrime[i]) {
                listPrimes.add(i);
                for (int j = 2; j * i < size; j++) {
                    isNotPrime[j * i] = true;
                }
            }
        }
        int length = listPrimes.size();
        int[] primes = new int[length];
        for (int i = 0; i < length; i++) {
            primes[i] = listPrimes.get(i) * listPrimes.get(i);
        }
        int[] values = new int[n + 1];
        for (int i = 1; i <= n; i++) {
            values[i] = i;
        }
        for (int i = 0; i < length; i++) {
            int base = 1;
            while (n / primes[i] >= base) {
                base *= primes[i];
                for (int j = 1; j * base <= n; j++) {
                    values[j * base] /= primes[i];
                }
            }
        }
        long ans = 0;
        for (int i = 1; i <= n; i++) {
            int tmp = (int)(Math.sqrt(i / values[i]));
            ans += tmp * 2 - 1;
        }
        System.out.println(ans);
    }
}

class Scanner {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer st = new StringTokenizer("");
    
    public Scanner() throws Exception {
        
    }
    
    public int nextInt() throws Exception {
        return Integer.parseInt(next());
    }
    
    public long nextLong() throws Exception {
        return Long.parseLong(next());
    }
    
    public String next() throws Exception {
        if (!st.hasMoreTokens()) {
            st = new StringTokenizer(br.readLine());
        }
        return st.nextToken();
    }
}