'''input

'''
import sys
import math
from bisect import bisect_right, bisect_left
from itertools import *
from collections import *
from heapq import heapify, heappush, heappop
import random
inf = float('inf')
# mod = 1000000007
# mod = 998244353
input = lambda: sys.stdin.readline().rstrip()
def error(*args, sep=' ', end='\n'):
  print(*args, sep=sep, end=end, file=sys.stderr)
# sys.setrecursionlimit(10**6)

#  -----------------------  #

n = int(input())
S = list(map(int, input().split()))
for i in range(n):
  S[i] -= 1
seen = [False] * n
cnt = 0
for i in range(n):
  if seen[i]:
    continue
  seen[i] = True
  f = i
  tmp = 0
  while True:
    i = S.index(i)
    seen[i] = True
    tmp += 1
    if i == f:
      break
  cnt += tmp-1

sgn = (-1) ** cnt
print(sgn)