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

FILE *in = fopen("fractii.in", "r");
FILE *out = fopen("fractii.out", "w");

const int N_MAX = 1e6 + 5;
int eras[N_MAX], n;
long long int sol = 1;

int main()
{
    fscanf(in, "%d", &n);

    for(int i = 1; i <= n; i ++)
        eras[i] = i - 1;
    for(int i = 2; i <= n; i ++)
    {
        for(int j = 2; i*j <= n; j++)
            eras[i*j] -= eras[i];
        sol += eras[i]*2;
    }
    fprintf(out, "%d", sol);
    return 0;
}