#include <stdio.h>
#define N 1000008

int e[N];
int a;

void euler(int n)
{
	int i,j;
	for(int i=2;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);
}


void afisare()
{
	for(int i=2;i<=a;++i)
		printf("%d ",e[i]);
}

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