#include<iostream>
#include <fstream>
using namespace std;
int n,s[1000001];
long long suma=0;

int main ()
{
    ifstream f("fractii.in");
    ofstream d("fractii.out");
    int i, j;
    f>>n;
    f.close();
    for( i=2 ; i<=n;  ++i ) s[i]=i-1;
    for( i=2 ; i<=n;  ++i )
    {
        suma+=s[i];
        for(j=i+i; j<=n ; j+=i ) s[j]-=s[i];
    }

    cout<<suma*2+1<<"\n";
    return 0;
}