#include <iostream>
#include <fstream>
using namespace std;

int main()
{
    ifstream in("fractii.in");ofstream out("fractii.out");
    int n,i,j;in>>n;int v[n];long long s=0;
    for(i=0;i<n;i++){v[i]=i+1;}
    for(i=1;i<n;i++){
        if(v[i]==i+1){v[i]--;
            for(j=2;(i+1)*j<=n;j++){
                v[(i+1)*j-1]=v[(i+1)*j-1]/(i+1)*i;}}
    }for(i=1;i<n;i++){s+=v[i];}s=2*s+1;out<<s;
    return 0;
}