#include <iostream>
#include <fstream>
using namespace std;
int cmmdc(int a,int b)
{
    int r=a%b;
    while(r)
    {
        a=b;
        b=r;
        r=a%b;
    }
    return b;
}

unsigned long long n,v[1000004],i,j,nr;
int main()
{
    ifstream f("fractii.in");
    ofstream g("fractii.out");
    //f>>n;
    cin>>n;
    for(i=1;i<=n;i++)
        v[i]=i;
  for(i=2;i<=n;i++)
    if(v[i]==i)
    {
        for(j=i;j<=n;j+=i)
            v[j]=v[j]-v[j]/i;
    }
    for(i=1;i<=n;i++)
        nr=nr+v[i];
    cout<<2*nr-1;
}