n = int(input())
if n == 0:
    print(0)
else:
    a = list(map(int, input().split()))
    max_len = 0
    left = 0
    last_occurrence = {}
    for right in range(len(a)):
        current = a[right]
        if current in last_occurrence and last_occurrence[current] >= left:
            left = last_occurrence[current] + 1
        last_occurrence[current] = right
        current_length = right - left + 1
        if current_length > max_len:
            max_len = current_length
    print(max_len)