#include<cstdio>
int e[1000001];



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