#include <bits/stdc++.h>
using namespace std;
ifstream fin("txt.in");
ofstream fout("txt.out");
#define ll long long
ll phi(ll n)
{
ll d=2,x=n;
while ( n>1 && d*d<=n )
{
if ( !n%d )
{
x/=d;
x*=(d-1);
while ( !n%d ) n/=d;
}
d++;
}
if ( n>1 ) x=x/n*(n-1);
return x;
}
int main()
{
ll n,s=1;
fin>>n;
for ( ll i=2; i<=n; i++ ) s+=2*phi(i);
fout<<s;
return 0;
}