#include<stdio.h>
long vector[1000100],n,i,j;
long long s;
int main()
{
	freopen("fractii.in","r",stdin);
	freopen("fractii.out","w",stdout);
	scanf("%ld",&n);
	for(i=1;i<=n;++i)
		vector[i]=i;
	for(i=2;i<=n;++i)
		if(vector[i]==i)
			for(j=i;j<=n;j+=i)
				vector[j]=vector[j]/i*(i-1);
	for(i=2;i<=n;++i)
		s=s+vector[i];
	printf("%lld\n",2*s+1);
	return 0;
}