#include<stdio.h>
#define N 1000128
#define RAD 45000
char ciur[N],eu[N];
int prime[N];
int n,nr=0;
void eratostene()
{
	int i,j;
	ciur[0]=ciur[1]=1;
	for(i=2;i*i<RAD;++i)
		if(!ciur[i])
		for(j=i<<1;j<RAD;j+=i)
			ciur[j]=1;
	for(i=2;i<RAD;++i)
		if(!ciur[i])
	prime[nr++]=i;

//for(i=0;i<nr;++i)
//printf("%d ",prime[i]);

}
int caut(int x)
{   //returneaza cel mai mic divizor prim al lui x
	for(int i=0;prime[i]*prime[i]<=x;++i)
	if(x%prime[i]==0)
		return prime[i];
	return x;
}
long long euler(int n)
{
	int i,p;
	long long s=1;
	eu[1]=1;
	for(i=2;i<=n;++i)
	{
		p=caut(i);
		if(i%(p*p)==0)
			eu[i]=eu[i/p]*p;
		else
			eu[i]=eu[i/p]*(p-1);
		s+=eu[i]<<1;
	}
	return s;
}
int main()
{
	freopen("fractii.in","r",stdin);
	freopen("fractii.out","w",stdout);
	scanf("%d",&n);
	eratostene();
	printf("%lld\n",euler(n));
	return 0;
}