#include <iostream>
#include <fstream>
#include <math.h>
using namespace std;
ifstream fin("fractii.in");
ofstream fout("fractii.out");
long long int p,n,b[1000000],i,j,k;
int main()
{
    fin>>n;
     for(i=2;i<=n;i++)
        b[i]=i;
     for(i=2;i<=n;i++)
        if(b[i]==i)
     {
         b[i]=i-1;
         for(j=2*i;j<=n;j=i+j)
            b[j]=b[j]-b[j]/i;
     }
            p=3;
             for(i=3;i<=n;i++)
                p=p+2*b[i];
             fout<<p;

    return 0;
}