n = int(input())
if n == 0:
    print(0)
    exit()
a = list(map(int, input().split()))

# Step 1: Split into groups of consecutive same values
groups = []
current_val = a[0]
current_count = 1
for num in a[1:]:
    if num == current_val:
        current_count += 1
    else:
        groups.append((current_val, current_count))
        current_val = num
        current_count = 1
groups.append((current_val, current_count))

# Step 2: Calculate same_max
from collections import defaultdict
value_sum = defaultdict(int)
for val, cnt in groups:
    value_sum[val] += cnt
same_max = max(value_sum.values()) if value_sum else 0

# Step 3: Calculate indep_max using dynamic programming
prev_no = 0
prev_yes = 0
for num in a:
    current_no = max(prev_no, prev_yes)
    current_yes = prev_no + 1
    prev_no, prev_yes = current_no, current_yes
indep_max = max(prev_no, prev_yes)

# Determine the result
print(max(same_max, indep_max))