#include<cstdio>
#define maxn 1000005

using namespace std;

typedef long long ll;

ll a[maxn],i,j,n,k;

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