#include <iostream>
#include <fstream>
#define MAXN 1000000
#define ll long long

using namespace std;
ifstream fin("fractii.in");
ofstream fout("fractii.out");
ll phi[MAXN];
int main(){
    ll n,s=0;
    fin>>n;
    for(ll i=1;i<=n;i++){
            phi[i]=i-1;
    }
    for(ll i=2;i<=n;i++){
        for(ll j=2*i;j<=n;j+=i)
            phi[j]-=phi[i];
        s+=2*phi[i];
    }
    fout<<s+1;
    return 0;
}