#include <iostream>
#include <fstream>
using namespace std;
ifstream fin("fractii.in");
ofstream fout("fractii.out");
long long int p,n,a[1000000],i,j;
int main()
{
    fin>>n;
    for(i=2;i<=n;i++)
    {
        a[i]=a[i]+1;
        if(a[i]==1)
        for(j=i+i;j<=n;j=j+i)
                a[j]=a[j]+((j-i)/i)*2;
    }
    p=2*2-1;
    for(int i=3;i<=n;i++)
        p=p+i-a[i]+i-1;
    fout<<p;
    return 0;
}