#include <bits/stdc++.h>
using namespace std;
ifstream in("fractii.in");
ofstream out("fractii.out");
int a[1000001];
int main()
{
	long long n,s=0,i,j;
	in>>n;
	for(i=2;i<=n;i++)
	{
		s+=(a[i]+=i-1);
		for(j=i*2;j<=n;j+=i)
			a[j]-=a[i];
	}
	out<<s*2+1;
	return 0;
}