import java.io.*;
import java.util.*;
import java.util.function.*;
import java.util.stream.*;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        int n = sc.nextInt();
        int[] values = new int[n + 1];
        for (int i = 1; i <= n; i++) {
            values[i] = i;
        }
        boolean[] isNotPrimes = new boolean[10000];
        for (int i = 2; i * i <= n; i++) {
            if (!isNotPrimes[i]) {
                for (int j = 2; j * i < isNotPrimes.length; j++) {
                    isNotPrimes[j * i] = true;
                }
                for (int j = 1; i * i * j <= n; j++) {
                    values[i * i * j] /= i * i;
                }
            }
        }
        int[] counts = new int[n + 1];
        for (int i = 1; i <= n; i++) {
            counts[values[i]]++;
        }
        long ans = 0;
        for (int x : counts) {
            ans += x * (x - 1L) / 2 * 2;
        }
        System.out.print(ans + n);
    }
}
class Scanner {
    BufferedReader br;
    StringTokenizer st = new StringTokenizer("");
    StringBuilder sb = new StringBuilder();
    
    public Scanner() {
        try {
            br = new BufferedReader(new InputStreamReader(System.in));
        } catch (Exception e) {
            
        }
    }
    
    public int nextInt() {
        return Integer.parseInt(next());
    }
    
    public long nextLong() {
        return Long.parseLong(next());
    }
    
    public double nextDouble() {
        return Double.parseDouble(next());
    }
    
    public String next() {
        try {
            while (!st.hasMoreTokens()) {
                st = new StringTokenizer(br.readLine());
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            return st.nextToken();
        }
    }
    
}