#include <bits/stdc++.h>
#define ll long long
using namespace std;
ifstream f("fractii.in");
ofstream g("fractii.out");
ll phi(ll n)
{
    ll x=n,i;
    for(i=2;i*i<=n;i++)
        if(!(n%i))
        {
            while(!(n%i))
                n/=i;
            x=(x/i)*(i-1);
        }
    if(n!=1) x=(x/n)*(n-1);
    return x;
}
int main()
{
    ll n,i,ans=1;
    f>>n;
    for(i=2;i<=n;i++)
        ans+=(2*phi(i));
    g<<ans;

    return 0;
}