#include<iostream>
#include<fstream>
#include<stdio.h>


using namespace std;
 
long long N, NFractii[1000005], S;
 
int main()
{
freopen ("fractii.in", "r", stdin);
freopen ("fractii.out", "w", stdout);
scanf ("%lld", &N);
for (int i=1; i<=N; ++i)
{
NFractii[i]=i;
S+=i;
}
for (int i=1; i<=N; ++i)
{
for (int j=2*i; j<=N; j+=i)
{
NFractii[j]-=NFractii[i];
S-=NFractii[i];
}
}
printf ("%lld\n", 2*S-1);
return 0;
}