#include <fstream>
#include <iostream>
#include <string>
#include <algorithm>
#include <vector>
#include <set>
#include <unordered_map>
#include <map>
#include <queue>
#include <stack>
#define N 1000006
#define ll long long
#define M 1000000007
#define PI 3.14159265
using namespace std;
ifstream in("fractii.in");
ofstream out("fractii.out");
ll f[N];
bool v[N];
int main(){
    int n,i,j;
    ll s=0;
    in>>n;
    for(i=2; i<=n; ++i){
        f[i]=i;
    }
    for(i=2; i<=n; ++i){
        if(!v[i]){
            for(j=i; j<=n; j+=i){
                v[j]=1;
                f[j]=f[j]/i*(i-1);
            }
        }
        s+=f[i];
    }
    out<<2*s+1;
    return 0;
}