#undef __STRICT_ANSI__
#include<bits/stdc++.h>
#define ll long long
using namespace std;
ifstream f("fractii.in");
ofstream g("fractii.out");
ll fi[5000001], k;
ll sum;
int n;
int main()
{
    f>>n;
    for(int j=1; j<=n; j++)
        fi[j]=j;

    for(int i = 2 ; i <= n ; i++)
    {
        if(fi[ i ] == i)
            for(int j = i  ; j <= n ; j += i)
            fi[ j ] = fi[ j ]/i * ( i - 1);
        sum += fi[ i ];
    }
    g << sum * 2 +1;

}