#include<cstdio>
using namespace std;
long long int s=1,n,i,j,phi[1000001];
int main(){
	freopen("fractii.in","r",stdin);
	freopen("fractii.out","w",stdout);
	scanf("%lld",&n);
	for(i=1;i<=n;++i){
		phi[i]=i-1;
	}
	for(i=2;i<=n;++i){
		for(j=2*i;j<=n;j+=i){
			phi[j]-=phi[i];
		}
	}
	for(i=n;i>0;--i){
		s+=2*phi[i];
	}
	printf("%lld\n",s);
	return 0;
}