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

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

int i,j,n;
int v[1000002];
//int v[12];

int main()
{
    v[1]=1;
    for(i=2;i<=1000002;i++)
        v[i]=i-1;
    for(i=2;i<=1000002;i++)
        for(j=2*i;j<=1000002;j+=i)
            v[j]-=v[i];
    /*for(i=1;i<=10;i++)
        cout<<i<< ' ' <<v[i]<< '\n';*/
    fin>>n;
    unsigned long long s=1;
    for(i=2;i<=n;i++)
        s+=v[i]*2;
    fout<< s << '\n';
    return 0;
}