#include <bits/stdc++.h>
using namespace std;
const long N = 2001;
long a[N];
int main() {
  ios::sync_with_stdio(0);
  long n;
  cin >> n;
  for (long i = 0; i < n; ++i) cin >> a[i];
  long res = 0;
  for (long k = 0; k <= n; ++k) {
    long l = k;
    long bestl = k;
    long score = 0;
    long highscore = 0;
    while (l > 0) {
      --l;
      if (a[l] == 2)
        ++score;
      else
        --score;
      if (score > highscore) {
        highscore = score;
        bestl = l;
      }
    }
    long r = k;
    long bestr = k;
    score = highscore = 0;
    while (r < n) {
      ++r;
      if (a[r - 1] == 1)
        ++score;
      else
        --score;
      if (score > highscore) {
        highscore = score;
        bestr = r;
      }
    }
    long cnt = 0;
    for (long i = 0; i < bestl; ++i)
      if (a[i] == 1) ++cnt;
    for (long i = bestl; i < k; ++i)
      if (a[i] == 2) ++cnt;
    for (long i = k; i < bestr and i < n; ++i)
      if (a[i] == 1) ++cnt;
    for (long i = bestr; i < n; ++i)
      if (a[i] == 2) ++cnt;
    res = max(res, cnt);
  }
  cout << res << endl;
}

### Prompt

Please create a solution in CPP to the following problem:

A dragon symbolizes wisdom, power and wealth. On Lunar New Year's Day, people model a dragon with bamboo strips and clothes, raise them with rods, and hold the rods high and low to resemble a flying dragon.

A performer holding the rod low is represented by a 1, while one holding it high is represented by a 2. Thus, the line of performers can be represented by a sequence a1, a2, ..., an.

Little Tommy is among them. He would like to choose an interval [l, r] (1 ≤ l ≤ r ≤ n), then reverse al, al + 1, ..., ar so that the length of the longest non-decreasing subsequence of the new sequence is maximum.

A non-decreasing subsequence is a sequence of indices p1, p2, ..., pk, such that p1 < p2 < ... < pk and ap1 ≤ ap2 ≤ ... ≤ apk. The length of the subsequence is k.

Input

The first line contains an integer n (1 ≤ n ≤ 2000), denoting the length of the original sequence.

The second line contains n space-separated integers, describing the original sequence a1, a2, ..., an (1 ≤ ai ≤ 2, i = 1, 2, ..., n).

Output

Print a single integer, which means the maximum possible length of the longest non-decreasing subsequence of the new sequence.

Examples

Input

4
1 2 1 2


Output

4


Input

10
1 1 2 2 2 1 1 2 2 1


Output

9

Note

In the first example, after reversing [2, 3], the array will become [1, 1, 2, 2], where the length of the longest non-decreasing subsequence is 4.

In the second example, after reversing [3, 7], the array will become [1, 1, 1, 1, 2, 2, 2, 2, 2, 1], where the length of the longest non-decreasing subsequence is 9.

### Response

```cpp
#include <bits/stdc++.h>
using namespace std;
const long N = 2001;
long a[N];
int main() {
  ios::sync_with_stdio(0);
  long n;
  cin >> n;
  for (long i = 0; i < n; ++i) cin >> a[i];
  long res = 0;
  for (long k = 0; k <= n; ++k) {
    long l = k;
    long bestl = k;
    long score = 0;
    long highscore = 0;
    while (l > 0) {
      --l;
      if (a[l] == 2)
        ++score;
      else
        --score;
      if (score > highscore) {
        highscore = score;
        bestl = l;
      }
    }
    long r = k;
    long bestr = k;
    score = highscore = 0;
    while (r < n) {
      ++r;
      if (a[r - 1] == 1)
        ++score;
      else
        --score;
      if (score > highscore) {
        highscore = score;
        bestr = r;
      }
    }
    long cnt = 0;
    for (long i = 0; i < bestl; ++i)
      if (a[i] == 1) ++cnt;
    for (long i = bestl; i < k; ++i)
      if (a[i] == 2) ++cnt;
    for (long i = k; i < bestr and i < n; ++i)
      if (a[i] == 1) ++cnt;
    for (long i = bestr; i < n; ++i)
      if (a[i] == 2) ++cnt;
    res = max(res, cnt);
  }
  cout << res << endl;
}

```