#include <iostream>
#include <fstream>
#define NMAX 1000005
std::ifstream in("fractii.in");
std::ofstream out("fractii.out");

using namespace std;
int n,sum[NMAX];
bool ciur[NMAX];
long long sumafin;
void era()
{
    for(int i=1;i<=n;i++)
    {
        sum[i]=i-1;
    }
    for(int i=2;i<=n;i++)
    {
        for(int j=i+i;j<=n;j+=i)
        {
            sum[j]-=sum[i];
            sumafin-=sum[i];
        }
    }
}

int main()
{
    in>>n;
    sumafin = (n*(n-1))/2;
    era();
    out<<sumafin*2+1;
    return 0;
}