#include<iostream>
using namespace std;

int main(){
	long long int sum=0,first, k,out=0;
	cin>>k;
	for(int i=k-1;i>0;i--){
		sum=sum+i;
	}
	first=((sum+1)*2)-1;
	for(int j=1;j<=k;j++){
		out=out+first;
		first+=2;
	}
	cout<<out;
	return 0;
}