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

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

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

int main()
{
    f>>n;
    for(i=2; i<=n; i++)
    {
        if(a[i]==0)
        {
            s=s+i-1;
            for(j=i*2; j<=n; j=j+i)
                if(a[j]!=0)
                    a[j]=a[j]-a[j]/i;
                else
                    a[j]=j-j/i;
        }
        else
            s=s+a[i];
    }
    g<<2*s+1;
    return 0;
}