#include <bits/stdc++.h>
using namespace std;
#define int long long
ifstream fin("fractii.in");
ofstream fout("fractii.out");
const int NMAX=1e6;
vector<int> phi(NMAX);
void build_phi(){
    phi[0]=0;
    phi[1]=1;
    for(int i=2;i<=NMAX;i++){
        phi[i]=i-1;
    }
    for(int i=2;i<=NMAX;i++){
        for(int j=2*i;j<=NMAX;j+=i){
            phi[j]-=phi[i];
        }
    }
}
signed main(){
    int n;
    fin>>n;
    build_phi();
    int s=0;
    for(int i=1;i<=n;i++){
        s+=2*phi[i];
    }
    fout<<s-1;
}