from collections.abc import Iterable
from enum import IntEnum, auto
from functools import cache
from unittest import case


class E(IntEnum):
    S = 0
    NONE = auto()
    APPLY = auto()

    def nexts(self):
        match self:
            case E.S: return [E.NONE, E.APPLY]
            case E.NONE: return [E.NONE, E.APPLY]
            case E.APPLY: return [E.APPLY, E.NONE]

        assert False

    @staticmethod
    @cache
    def states():
        res = []
        for fm in E:
            for to in fm.nexts():
                res.append((fm, to))

        return res


def state_dp(xs: Iterable, op, e, init: dict, *, is_reset=True):
    dp = [e] * len(E)
    for k, v in init.items():
        dp[k] = v

    for x in xs:
        pp = [e] * len(E) if is_reset else dp.copy()
        dp, pp = pp, dp
        for fm, to in E.states():
            if not is_valid(to, pp[fm], x): continue
            dp[to] = op(to, dp[to], fm, pp[fm], x)

    return dp


def is_valid(to: E, fm_v, v) -> bool:
    return True


def op(to: E, to_v, fm: E, fm_v, v):
    ma, size = fm_v
    match to:
        case E.NONE:
            return max(to_v, (ma, v))

        case E.APPLY:
            if fm == E.APPLY:
                if size == v:  # 同じ大きさなら消滅しない
                    return max(to_v, (ma+1, size))
                else:
                    return max(to_v, (ma, max(size, v)))
            else:
                return max(to_v, (ma+1, v))

    assert False


N = int(input())
A = list(map(int, input().split()))

dp = state_dp(A, op, (0, -1), {E.S: (0, -1)})
ans = max(ma for ma, _ in dp)
print(ans)