#!/bin/python

import sys

def sumOfGroup(k):
    ans = 0;
    if k==1 :
        ans = 1
    else:
        ans = (k*k) - (k-1) 
    tmp = 0
    #print ans
    for _ in range(0,k):
        #print ans
        tmp = tmp + ans;
        ans = ans + 2
    return tmp
if __name__ == "__main__":
    k = int(raw_input().strip())
    answer = sumOfGroup(k)
    print answer