#include <bits/stdc++.h>
using namespace std;
int phi[1000002];
int main() {
     unsigned long long num =0;
     int n;
     cin >> n;
     phi[0] = 0;
     phi[1] = 1;
     for(int i =2; i<= n ; i++){
        phi[i] = i-1;
     }
     for(int i =2 ; i<= n ; i++){
        for(int j = i*2 ; j<= n ; j+=i){
            phi[j]-=phi[i];
        }
     }
     for(int i =2; i<= n ; i++){
        num+=2*phi[i];
     }
     cout << num+1;

    return 0;
}