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