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);
        }
        long ans = 0;
        for (int i = 1; i <= n; i++) {
            int x = i;
            int count = 1;
            for (int j = 0; j < length && primes[j] <= x; j++) {
                while (x % primes[j] == 0) {
                    count++;
                    x /= primes[j];
                }
            }
            ans += count * 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();
    }
}