#include <stdio.h>
#include <vector>
using namespace std;


int n;
vector<int> phi;

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