import collections
#import time

#start = time.time()

def solve(N, As):
    As = compress(As)
    if len(As) < 3:
        return 0
    if len(set(As)) < 7:
        return solve_small(As)
    LH = [set([float('inf')])]
    maxLH = [float('inf')]
    LHprev = collections.defaultdict(int)
    LHrank = collections.defaultdict(int)
    LHprev[float('inf')] = -float('inf')
    LHrank[float('inf')] = 0
    
    HL = [set([-float('inf')])]
    minHL = [-float('inf')]
    HLprev = collections.defaultdict(int)
    HLrank = collections.defaultdict(int)
    HLprev[-float('inf')] = float('inf')
    HLrank[-float('inf')] = 0
    
    for a in As:
        update_data(a, True, LH, maxLH, LHprev, HL, minHL, HLrank, HLprev)
        update_data(a, False, HL, minHL, HLprev, LH, maxLH, LHrank, LHprev)
    
    return max(len(LH), len(HL)) - 1


def update_data(a, dLOW, LH, maxLH, LHprev, HL, minHL, HLrank, HLprev):
    '''dLOW: True  -> a をHL に追加しようとしている。
             False -> a をLH に追加しようとそている。
       LH, HL 等は、dLOW = True の場合の変数名。呼び出し側で適宜入れ替える。
    '''
    LHmax = len(LH) - 1
    for k in range(LHmax, - 1, -1):
        if k + 1 < HLrank[a]:
            break
        if (dLOW and maxLH[k] <= a) or (not dLOW and maxLH[k] >= a):
            continue
        for b in LH[k]:
            if (dLOW and b <= a) or ((not dLOW) and b >= a) or LHprev[b] == a:
                continue
            if HLrank[a] == k + 1:
                if (dLOW and a < minHL[k + 1]) or ((not dLOW) and a > minHL[k + 1]):
                    minHL[k + 1] = a
                if HLprev[a] != b:
                    HLprev[a] = -1
                break
            else:
                HLrank[a] = k + 1
                HLprev[a] = b
                lenHL = len(HL)
                if k == lenHL:
                    HL.append(set())
                    HL.append(set([a]))
                    dummy = float('inf') if dLOW else -float('inf')
                    minHL.append(dummy)
                    minHL.append(a)
                elif k + 1 == lenHL:
                    HL.append(set([a]))
                    minHL.append(a)
                elif k + 1 < lenHL:
                    HL[k + 1].add(a)
                    if  (dLOW and a < minHL[k + 1]) or ((not dLOW) and a > minHL[k + 1]):
                        minHL[k + 1] = a

def compress(As):
    Bs = [As[0]]
    b = As[0]
    for a in As[1:]:
        if a != b:
            Bs.append(a)
            b = a
    return Bs

    
def solve_small(As):
    dp = collections.defaultdict(int)
    dp[float('inf'), -float('inf')] = 0
    dp[-float('inf'), float('inf')] = 0
    for a in As:
        for (b, c), val in list(dp.items()):
            if c != a and ((a > b and b < c) or (a < b and b > c)):
                dp[a, b] = max(val + 1, dp[a, b])
    return max(dp.values())

N = int(input())
As = list(map(int, input().split()))
ans = solve(N, As)
if ans < 3:
    print(0)
else:
    print(ans)