n = int(input())
permutation = list(map(int, input().split()))
visited = [False] * n
count = 0

for i in range(1, n + 1):
    if not visited[i - 1]:
        current = i
        cycle_length = 0
        while not visited[current - 1]:
            visited[current - 1] = True
            current = permutation[current - 1]
            cycle_length += 1
        count += (cycle_length - 1)

sign = 1 if count % 2 == 0 else -1
print(sign)