#include<stdio.h>
#define N 1000000
int e[N];
int main()
{
	 long long n,i,j,s;
	 freopen("fractii.in","r",stdin);
	 freopen("fractii.out","w",stdout);
	 scanf("%lld",&n);
	 for(j=2;j<=n;j++)
		 e[j]=j;
	 for(i=2;i<=n;i++)
	 {
		 if (e[i]==i)
			 for(j=i*i;j<=n;j+=i)
				 e[j]=e[j]/i*(i-1);
	 }
	s=0;
	 for(i=2;i<=n;i++)
		s=s+2*e[i];
	
	s=s+1;
	printf("%lld\n",s);
	return 0;
}