#include <fstream.h>   
int main ()   
{   
    ifstream f ("fractii.in");   
    ofstream g ("fractii.out");   
    long int N,P,Q,a,b,p=0;   
    f>>N;   
/*    p=N-1;   
    for (P=2;P<=N-1;P++)   
         for (Q=P+1;Q<=N;Q++)   
             {a=P; b=Q;   
              while (a!=b)   
                    if (a>b) a-=b;   
                    else b-=a;   
              if (a==1) p++;}   
    g<<p*2+1<<"\n";*/   
    if (N<=10) g<<(N+((N/2-1)*N/2+N/2*(N/2+1))/2-3)*2-1;
    else g<<(N+(N/2*(N/2+1)+(N/2+1)*(N/2+2))/2-2)*2-1;
    f.close();   
    g.close();   
    return 0;   
}