#include <fstream>

using namespace std;

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

int n,i,j;
int v[1000001];
long long ans;

int main()
{
    fin>>n;
    for(i=1;i<=n;i++)
        v[i]=i-1;
    ans=1;
    for(i=2;i<=n;i++)
        for(j=i*2;j<=n;j+=i)
            v[j]-=v[i];
    for(i=2;i<=n;i++)
        ans+=v[i]*2;
    fout<<ans;
}