#include<cstdio>
#include<algorithm>
#include<cstring>
#define nmax 1000000
using namespace std;
int n,i,j,k,x,y,m;
int phi[nmax+1];
long long rez;

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