import sys
input = sys.stdin.readline
print = sys.stdout.write

N = int(input())
tanghuru = list(map(int, input().split()))
fruit_count = {}
start = end = 0
maxLen = 0

while True :
    if  len(fruit_count) <= 2 :
        maxLen = max(maxLen, end - start)
        if end == N :
            break
        fruit_count[tanghuru[end]] = fruit_count.get(tanghuru[end],0) + 1
        end += 1
    else :
        fruit_count[tanghuru[start]] -= 1
        if fruit_count[tanghuru[start]] == 0 :
            fruit_count.pop(tanghuru[start])
        start += 1

print(str(maxLen)+'\n')