#include<stdio.h>
long f[1000005];
int main()
{
	freopen("fractii.in","r",stdin);
	freopen("fractii.out","w",stdout);
	long n,i,j;
	long long s=0;
	scanf("%ld",&n);
	for(i=1;i<=n;++i)
		f[i]=i;
	for(i=2;i<=n;++i)
		if(f[i]==i)
			for(j=i;j<=n;j+=i)
				f[j]=f[j]/i*(i-1);
	for(i=2;i<=n;++i)
		s+=f[i];
	s=2*s+1;
	printf("%I64d\n",s);
	return 0;
}