#include<fstream.h>
long long N;
long long nr(){
long long S=1;
for (long long i=1;i<N;i++)
    S+=i;
return S;
}
int main(){
ifstream fin("sarpe.in");
ofstream fout("sarpe.out");
fin>>N;
fout<<nr()*4;
fout<<"\n";
fin.close();
fout.close();
return 0;
}