#include<bits/stdc++.h>
#define pb push_back
#define NAX 101
#define MOD 7
using namespace std;
using ll = long long;

ifstream f("fractii.in");
ofstream g("fractii.out");


long long sol, n, v[1000001];

int main()
{
    ios_base::sync_with_stdio(0);
    f.tie(0);
    f >> n;
    for(int i = 1 ; i <= n ; ++i)
        v[ i ] = i;
    for(int i = 2 ; i <= n ; ++i)
    {
        if( v[ i ] == i)
            for(int j = i ; j <= n ; j += i)
                v[ j ] = v[ j ]/i * ( i - 1 );
        sol += v[ i ];
    }
    g << sol * 2 + 1;
    return 0;
}