import sys
input = sys.stdin.readline
sys.setrecursionlimit(10 ** 6)
def II(): return int(sys.stdin.readline())
def LI(): return list(map(int, sys.stdin.readline().split()))
def LC(): return list(input())
def IC(): return [int(c) for c in input()]
def MI(): return map(int, sys.stdin.readline().split())
INF = float('inf')
MOD = 10**9 + 7
def solve():
    K = II()
    if(K==1):
        print(6)
        exit()
    elif(K==2):
        print(18)
        exit()
    #少なくとも、(2K-3)**2以上
    Ans = (2*K-3)**2 + 6*K-7 + K +2*K+1 + 2*(K-1) + K+1
    print(Ans)
    return
solve()