#include <iostream>

using namespace std;

int main()
{
    int n,s=0,v[21];
    cin>>n;
    for (int i=1;i<=n;i++)
        v[i]=i;
    for (int i=2;i<=n;i++)
        if (v[i] == i)
            for (int j=i;j<=n;j+=i)
                v[j]=v[j]*(i-1)/i;
    for (int i=2;i<=n;i++)
        s+=v[i];
    s*=2;
    s++;
    cout<<s;



    return 0;
}