n = int(input())
if n == 0:
    print(0)
    exit()
arr = list(map(int, input().split()))
last_occurrence = {}
max_length = 0
left = 0

for right in range(n):
    current = arr[right]
    if current in last_occurrence:
        # Ensure left pointer moves to the right of the last occurrence of current
        left = max(left, last_occurrence[current] + 1)
    # Update the last occurrence of the current element
    last_occurrence[current] = right
    # Calculate the current window length and update max_length
    current_length = right - left + 1
    if current_length > max_length:
        max_length = current_length
print(max_length)