#include <cstdio>

using namespace std;

int v[1000005];

int main()
{
	int n,i,j;
	long long sol;
	freopen ("fractii.in","r",stdin);
	freopen ("fractii.out","w",stdout);
	scanf("%d", &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);
			}
	sol=0;
	for(i=1;i<=n;i++)
		sol+=v[i];
	sol=sol*2-1;
	printf("%lld\n", sol);
	return 0;
}