#include <iostream>
#include <fstream>
#include <cstdio>
using namespace std;
ofstream g("fractii.out");
int N,j,n,nr,i,a[2000010];
long long r;
int main()
{
    freopen("fractii.in","r",stdin);
    scanf("%d",&N);
    for (i=2;i<= N;i++)
        a[i] = i;
    for (i=2;i<=N;i++)
        if(a[i]==i)
        {
            for(j= i;j<=N;j+=i)
                a[j]=a[j]/i*(i-1);
        }
    for (i=1;i<=N;i++)
        r+=a[i];
    r=r*2;
    r+=1;
   /* for ( i = 1; i <= N; i++ )
        fout << a[i] << ' ';
    fout << '\n'; */
    g<<r;
    return 0;
}