#include<stdio.h>
int f(int n){
	if(n==1){
		return 2;
	}else{
		return f(n-1) + 2*(n-1);
	}
}
void main(){
	int n;
	scanf("%d",&n);
	printf("%d",f(n));
}

/**************************************************************
	Problem: 1366
	User: admin
	Language: C
	Result: Accepted
	Time:18 ms
	Memory:1172 kb
****************************************************************/