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python
a year ago
767 B
1
Indexable
Never
def solve(arr, a, b):
    set2 = set()
    map = {}
    t = a
    c = 1
    while True:
        if t in map:
            break
        if t == -1:
            break
        map[t] = c
        c += 1
        t = arr[t]

    t = b
    j = 0
    minimum = float('inf')
    ans = -1
    while True:
        if t in set2:
            break
        if t == -1:
            break
        if map[t] == 0:
            j += 1
            set2.add(t)
            t = arr[t]
            continue
        summation = map[t] + j
        if summation < minimum:
            minimum = summation
            ans = t
        set2.add(t)
        t = arr[t]
    return ans


n = int(input())
arr = list(map(int, input().split()))
a, b = map(int, input().split())
print(solve(arr, a, b))