#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])
        {
            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];
    g<<2*s+1;
}