#include<stdio.h>
#define N 1000005
#define RAD 1100
int eu[N],prime[RAD],ciur[RAD],nr,n;
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));
	fclose(stdin);
	fclose(stdout);
	return 0;
}