n = int(input())
a = list(map(int, input().split()))

# Calculate max_same
from collections import defaultdict
max_same = 0
current_val = None
current_length = 0
count = defaultdict(int)

for num in a:
    if num == current_val:
        current_length += 1
    else:
        if current_val is not None:
            count[current_val] += current_length
        current_val = num
        current_length = 1
# Add the last segment
if current_val is not None:
    count[current_val] += current_length

if count:
    max_same = max(count.values())
else:
    max_same = 0

# Calculate max_non_adjacent using House Robber approach
prev1, prev2 = 0, 0
for _ in a:
    current = max(prev1, prev2 + 1)
    prev2, prev1 = prev1, current
max_non_adjacent = prev1

# Determine the answer
print(max(max_same, max_non_adjacent))