#include<stdio.h>

int n,e[1000001];
long long sum;

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