#include<bits/stdc++.h>
using namespace std;
#define INIT  ios_base :: sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
#define mp make_pair
#define pb push_back
#define ft first
#define sc second
#define ll long long
#define pii pair<int, int>
#define count_bits __builtin_popcount
#define int ll

int t, n, fi[1000010];
bool v[1000010];
ifstream fin("fractii.in"); ofstream fout("fractii.out");
#define cin fin
#define cout fout


int32_t main(){
INIT
cin>>n;
int res=0;
for(int i=2; i<=n; i++){
    if(!v[i]){
        v[i]=true;
        fi[i]=i-1;
        for(int j=i*i; j<=n; j*=i){
            v[j]=true;
            fi[j]=(j-j/i);
        for(int g=2;(j*g<=n); g++){
            if(g%i==0){continue;}
            v[j*g]=true;
            fi[j*g]=fi[j]*fi[g];}
        }
        for(int j=2;(i*j<=n); j++){
            if(j%i==0){continue;}
            v[i*j]=true;
            fi[i*j]=fi[j]*fi[i];}
        }



    //cout<<fi[i]<<" ";
    res+=2*fi[i];
}
cout<<res+1;



return 0;
}