#!/bin/python

import sys

def sumOfGroup(k):
    lis=[]
    num=k*(k-1)+1
    lis.append(num)
    for i in range(k-1):
        num=num+2
        lis.append(num)
    return sum(lis)
        
    # Return the sum of the elements of the k'th group.

if __name__ == "__main__":
    k = int(raw_input().strip())
    answer = sumOfGroup(k)
    print answer