#!/bin/python

import sys

def getNextNOdd(ix, n):

	return list( x for x in xrange(ix,2*n + ix - 1 ) if x % 2 == 1)

# def sumOfGroup(ix,nxt,k):
#     # Return the sum of the elements of the k'th group.
#     if nxt == k:
#         return sum(getNextNOdd(ix,k))
#     res = getNextNOdd(ix, nxt) 
#     #print res
#     ix = res[-1] + 2
#     nxt = nxt + 1
#    # print ix, nxt
#     return sumOfGroup(ix,nxt,k)
    
def sumOfGroup2(k):
	finished = False
	ix = 1
	nxt = 1
	s = 0
	while finished == False:
		if nxt == k:
			#print "done!"
			finished = True
			s = sum(getNextNOdd(ix,k))
		else:
			#print "tesr"
			res = getNextNOdd(ix, nxt) 
			#print res
			ix = res[-1] + 2
			nxt = nxt + 1

	return s

if __name__ == "__main__":
    k = int(raw_input().strip())
    #answer = sumOfGroup(1,1,k)
    answer = sumOfGroup2(k)
    print answer