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