#include<bits/stdc++.h>
using namespace std;
#define LL long long
#define ULL unsigned long long
vector <LL> v;
int main()
{   LL k,i;
    cin>>k;
    v.push_back(0);
    v.push_back(1);
    for(i=2;i<=k;i++)
      v.push_back((i-1)*2 + v[i-1]);
    LL sum = v[k];
    //cout<<v[k]<<endl;
    for(i=1;i<k;i++)
        sum = sum + (v[k]+i*2);
    cout<<sum<<endl;


}