#include <bits/stdc++.h>
#define ll long long
using namespace std;

int const maxim=1000010;
ll vector1[maxim];
ll contor=0;

void eliminare_multiplii(int n){
	for(int i=0;i<=n;i++)vector1[i]=i-1;
	for(int i=2;i<=n;i++){
		contor+=vector1[i];
		if(vector1[i]==i-1)
		for(int j=i;j>0 && j<=n;j+=i){
			int c=vector1[j]/i;
			vector1[j]-=c;
		}
	}
}

int main(){
	int n;
	ifstream cin("fractii.in");
	ofstream cout("fractii.out");
	cin>>n;
	eliminare_multiplii(n);
	cout<<contor*2+1;
	return 0;
}