#include <fstream>
#include <cmath>

using namespace std;

ifstream in("fractii.in");
ofstream out("fractii.out");

long long unsigned int s=0,a[1000000],j,n,i;

int main()
{   in>>n;

    for(i=2;i<=n;i++)
        if(!a[i])
        {
            s+=i-1;

            for(j=i*2;j<=n;j+=i)
                if(a[j])    a[j]-=a[j]/i;
                else a[j]=j-j/i;
        }
        else s+=a[i];

    out<<2*s+1;




    in.close();
    out.close();
    return 0;
}