#include<cstdio>
#define N 1000001
long long s=0,e[N];
long long  i,n;
void era(int n)
{
	long long i,j;
	for(i=2;i<=n;++i)
		e[i]=i;
	for(i=2;i<=n;++i)
		if(e[i]==i)
		for(j=i;j<=n;j=j+i)
			e[j]=e[j]/i*(i-1);
}
int main()
{
	freopen("fractii.in","r",stdin);
	freopen("fractii.out","w",stdout);
	
	scanf("%lld",&n);
	era(n);
	for(i=2;i<=n;++i)
		s+=e[i];
	printf("%lld",2*s+1);
	return 0;
}