tijie

#include<bits/stdc++.h>
using namespace std;
#define N 100001
int a[N],n;
int main(){
	cin>>n;
	a[1]=3,a[2]=9;
    for(int i=3;i<=n;i++){
        a[i]=a[i-1]+4*i-2;
    }
    cout<<a[n];
	return 0;
}