from collections import defaultdict


N = int(input())
A = list(map(int, input().split()))
ans = 0
counter = defaultdict(int)
r = 0
for l in range(N):
    while r < N and (not counter[A[r]]):
        counter[A[r]] += 1
        r += 1
    ans = max(ans, r-l)
    counter[l] -= 1
print(ans)