#include <bits/stdc++.h>
using namespace std;
const int N = 10010;
int a[N], b[N][3], c[N];
int main() {
  int n;
  cin >> n;
  for (int i = 1; i <= n; i++) {
    cin >> a[i];
    b[i][1] = b[i - 1][1];
    b[i][2] = b[i - 1][2];
    b[i][a[i]]++;
  }
  int res = max(b[n][1], b[n][2]);
  for (int i = 1; i <= n; i++) res = max(res, b[i][1] + b[n][2] - b[i][2]);
  for (int i = 1; i <= n; i++) {
    c[i] = max(b[n][1] - b[i - 1][1], b[n][2] - b[i - 1][2]);
    for (int j = i; j <= n; j++)
      c[i] = max(c[i], b[j][1] - b[i - 1][1] + b[n][2] - b[j][2]);
  }
  for (int i = 1; i <= n; i++) {
    for (int j = i; j <= n; j++) {
      res = max(res, b[i - 1][1] + b[j][2] - b[i - 1][2] + c[j + 1]);
    }
  }
  cout << res;
  return 0;
}

### Prompt

Construct a cpp code solution to the problem outlined:

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 int N = 10010;
int a[N], b[N][3], c[N];
int main() {
  int n;
  cin >> n;
  for (int i = 1; i <= n; i++) {
    cin >> a[i];
    b[i][1] = b[i - 1][1];
    b[i][2] = b[i - 1][2];
    b[i][a[i]]++;
  }
  int res = max(b[n][1], b[n][2]);
  for (int i = 1; i <= n; i++) res = max(res, b[i][1] + b[n][2] - b[i][2]);
  for (int i = 1; i <= n; i++) {
    c[i] = max(b[n][1] - b[i - 1][1], b[n][2] - b[i - 1][2]);
    for (int j = i; j <= n; j++)
      c[i] = max(c[i], b[j][1] - b[i - 1][1] + b[n][2] - b[j][2]);
  }
  for (int i = 1; i <= n; i++) {
    for (int j = i; j <= n; j++) {
      res = max(res, b[i - 1][1] + b[j][2] - b[i - 1][2] + c[j + 1]);
    }
  }
  cout << res;
  return 0;
}

```