#include <iostream>
#include <fstream>
using namespace std;
ifstream f("fractii.in");
ofstream g("fractii.out");
int main()
{
    long int n,i,j;
    long long nr=0;
    f>>n;
    long int v[n];
    for(i=1;i<=n;i++)
        v[i]=i-1;
    for(i=2;i<=n;i++)
    {nr+=v[i];
        for(j=2*i;j<=n;j+=i)
            v[j]-=v[i];}
    g<<2*nr+1;
    f.close();g.close();
    return 0;
}