//
//  main.cpp
//  test
//
//  Created by Alex Clapa on 10.06.2012.
//  Copyright (c) 2012 __MyCompanyName__. All rights reserved.
//

#include <stdio.h>

const int N = 1000005;

int e[N];
int sol = 1;

int main()
{
    freopen("fractii.in","r",stdin);
    freopen("fractii.out","w",stdout);
    
    int n;
    
    scanf("%d", &n);
    
    for(int i=1;i<=n;i++)
        e[i] = i;
    for(int i=2;i<=n;i++) {
        if(e[i] == i)
            for(int j=i;j<=n;j+=i)
                e[j] = e[j]/i * (i-1);
        sol+=2*e[i];
    }
    
    printf("%d\n", sol);
    
    return 0;
}