Problem: As you could know there are no male planes nor female planes. However, each plane on Earth likes some other plane. There are n planes on Earth, numbered from 1 to n, and the plane with number i likes the plane with number fi, where 1 ≤ fi ≤ n and fi ≠ i.

We call a love triangle a situation in which plane A likes plane B, plane B likes plane C and plane C likes plane A. Find out if there is any love triangle on Earth.

Input

The first line contains a single integer n (2 ≤ n ≤ 5000) — the number of planes.

The second line contains n integers f1, f2, ..., fn (1 ≤ fi ≤ n, fi ≠ i), meaning that the i-th plane likes the fi-th.

Output

Output «YES» if there is a love triangle consisting of planes on Earth. Otherwise, output «NO».

You can output any letter in lower case or in upper case.

Examples

Input

5
2 4 5 1 3


Output

YES


Input

5
5 5 5 5 1


Output

NO

Note

In first example plane 2 likes plane 4, plane 4 likes plane 1, plane 1 likes plane 2 and that is a love triangle.

In second example there are no love triangles.

Solution (in PYTHON3):

Solution:
#~~~~~~~~~~~~~~~    JAI SHREE RAM    ~~~~~~~~~~~~~~~~~~#

import math; from collections import *
import sys; from functools import reduce

# sys.setrecursionlimit(10**6)

def get_ints(): return map(int, input().strip().split())
def get_list(): return list(get_ints())
def get_string(): return list(input().strip().split())
def printxsp(*args): return print(*args, end="")
def printsp(*args): return print(*args, end=" ")

DIRECTIONS = [[0, 1], [0, -1], [1, 0], [1, -1]] #up, down, right, left
NEIGHBOURS = [(i, j) for i in range(-1, 2) for j in range(-1, 2) if (i!=0 or j!=0)]

OrdUnicode_a = ord('a'); OrdUnicode_A = ord('A')
CAPS_ALPHABETS = {chr(i+OrdUnicode_A) : i for i in range(26)}
SMOL_ALPHABETS = {chr(i+OrdUnicode_a) : i for i in range(26)}

UGLYMOD = int(1e9)+7; SEXYMOD = 998244353; MAXN = int(1e5)+1; INFINITY = float('inf')

# sys.stdin=open("input.txt","r");sys.stdout=open("output.txt","w")

# for _testcases_ in range(int(input())):
n = int(input())
li = get_list()
li.insert(0, 0)
flag = False
for i in range(1, n):
    if i == li[li[li[i]]]:
        flag = True
print("YES" if flag else "NO")




'''
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'''