#include<stdio.h>
int n,i,j,p,a[1000001];
long long S;
void read(),solve();
int main()
{
	read();
	solve();
	return 0;
}
void read()
{
	freopen("fractii.in","r",stdin);
	freopen("fractii.out","w",stdout);
	scanf("%d",&n);
}
void solve()
{
	for(i=2;i<=n;i++)a[i]=i-1;
	for(i=2;i<=n;i++)
	{
		S+=a[i];
		for(j=i+i;j<=n;j+=i)a[j]-=a[i];
	}
	S*=2;S++;
	printf("%lld\n",S);
}