/*
	 n=6
	 1/1 1/2 1/3 1/4 1/5 1/6
	 2/1 2/3 2/5 2/6
	 3/1 3/2 3/4 3/5
	 4/1 4/3 4/5
	 5/1 5/2 5/3 5/4 5/6
	 6/1 6/5
		=> k=21
*/
#include<stdio.h>
long c[1000010];
int main()
{
freopen("fractii.in","r",stdin);
freopen("fractii.out","w",stdout);
int n,i,j;
long long s=0;
scanf("%d",&n);
for(i=1;i<=n;i++)
	c[i]=i;
for(i=2;i<=n;i++)
	if(c[i]==i)
		for(j=i;j<=n;j+=i)
			c[j]=c[j]/i*(i-1);
for(i=1;i<=n;i++)
	s=s+c[i];
s=s*2-1;
printf("%lld\n",s);
return 0;
}