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