While playing with geometric figures Alex has accidentally invented a concept of a $n$-th order rhombus in a cell grid.

A $1$-st order rhombus is just a square $1 \times 1$ (i.e just a cell).

A $n$-th order rhombus for all $n \geq 2$ one obtains from a $n-1$-th order rhombus adding all cells which have a common side with it to it (look at the picture to understand it better).

 [Image] 

Alex asks you to compute the number of cells in a $n$-th order rhombus.


-----Input-----

The first and only input line contains integer $n$ ($1 \leq n \leq 100$) — order of a rhombus whose numbers of cells should be computed.


-----Output-----

Print exactly one integer — the number of cells in a $n$-th order rhombus.


-----Examples-----
Input
1

Output
1
Input
2

Output
5
Input
3

Output
13


-----Note-----

Images of rhombus corresponding to the examples are given in the statement.

Difficulty: interview

Starter code:

Solutions:
n = int(input())
a = n * (n + 1) // 2
print(4 * a - 4 * n + 1)

n=int(input())
print(int(n**2+(n-1)**2))

n = int(input())
ans = 1
for i in range(1, n):
    ans += i * 4
print(ans)

n = int(input())
ans = 1
for i in range(n):
    ans += i * 4
print(ans)

a = int(input())
print(a * (a - 1) * 2 + 1)

a = int(input())

print(a**2+(a-1)**2)


n=int(input())-1
print(2*n*(n+1)+1)


def getN():
    return int(input())
def getList():
    return list(map(int, input().split()))

n = getN()
mid = n * 2 -1
ans = -mid
while(mid > 0):
    ans += mid*2
    mid -= 2

print(ans)

n = int(input())
print(n**2 + (n-1)**2)


n = int(input())
summ = 1
for i in range(1, n):
    summ+=i*4
print(summ)

n = int(input())
print(n**2+((n-1)**2))


n = int(input())
ans = 1
for i in range(n):
    ans += 4 * i
print(ans)



import math
import sys

#imgur.com/Pkt7iIf.png

#n, m = map(int, input().split())
#n = int(input())
#d = list(map(int, input().split()))

n = int(input())
r = 0
t = 1
for i in range(n-1):
    r += t*2
    t += 2
print(r + t)


n=int(input())
print(n**2+(n-1)**2)

n = int(input())
wyn = 1
x = 4
for i in range(n - 1):
	wyn += x
	x += 4
print(wyn)

# coding: utf-8
import sys
sys.setrecursionlimit(int(1e7))

def main():
    n = int(input().strip())
    print(2*(n*(n-1))+1)
    return

while 1:
    try: main()
    except EOFError: break

n=int(input())
answer=0
for i in range(1,2*n-2,2):
    answer+=i
print(answer*2+2*n-1)


n=int(input())
print(2*n*n-2*n+1)

def main():
    n = int(input())
    ans = n * n + (n - 1) * (n - 1)
    print(ans)


def __starting_point():
    main()

__starting_point()

n = int(input())
ans = (2 * (n - 1) ** 2) + 2 * n - 1
print(ans)


n = int(input())
print(1+2*((n-1)*n))


n = int(input())
cur = 1
for i in range(n-1):
    cur+=4*(i+1)
print(cur)


n = int(input().strip())
print(n**2+(n-1)**2)

a= int(input())
ans = 1
k = 4
for i in range(a - 1):
    ans += k
    k += 4
if a == 0:
    print(0)
else:
    print(ans)