#include<stdio.h>
const int N=1000005;
int n,e[N];
void euler(int n)
{
	int i,j;
	for(i=1;i<=n;i++)
		e[i]=i;
	for(i=2;i<=n;i++)
		if(e[i]==i)
			for(j=i;j<=n;j+=i)
				e[j]=e[j]/i*(i-1);
}

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