#include <bits/stdc++.h>
using namespace std;
long long int arr[100001], sum1[100001], sum2[100001];
int main() {
  ios::sync_with_stdio(false);
  ;
  cin.tie(0);
  ;
  long long int i, j, n, ans = -1000000000000, maxi, l, r;
  cin >> n;
  for (i = 1; i <= n; i++) {
    cin >> arr[i];
    sum1[i] = sum1[i - 1] + (arr[i] == 1);
    sum2[i] = sum2[i - 1] + (arr[i] == 2);
  }
  ans = sum1[n];
  ans = max(ans, sum2[n]);
  for (i = 1; i <= n; i++) ans = max(ans, sum1[i] + sum2[n] - sum2[i]);
  for (l = 1; l <= n; l++) {
    maxi = -1000000000000;
    for (r = l; r <= n; r++) {
      maxi = max(maxi, sum2[r] - sum1[r]);
      ans = max(ans,
                sum1[l - 1] + sum2[n] - sum2[r] + sum1[r] - sum2[l - 1] + maxi);
    }
  }
  cout << ans;
  return 0;
}

### Prompt

Develop a solution in Cpp to the problem described below:

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;
long long int arr[100001], sum1[100001], sum2[100001];
int main() {
  ios::sync_with_stdio(false);
  ;
  cin.tie(0);
  ;
  long long int i, j, n, ans = -1000000000000, maxi, l, r;
  cin >> n;
  for (i = 1; i <= n; i++) {
    cin >> arr[i];
    sum1[i] = sum1[i - 1] + (arr[i] == 1);
    sum2[i] = sum2[i - 1] + (arr[i] == 2);
  }
  ans = sum1[n];
  ans = max(ans, sum2[n]);
  for (i = 1; i <= n; i++) ans = max(ans, sum1[i] + sum2[n] - sum2[i]);
  for (l = 1; l <= n; l++) {
    maxi = -1000000000000;
    for (r = l; r <= n; r++) {
      maxi = max(maxi, sum2[r] - sum1[r]);
      ans = max(ans,
                sum1[l - 1] + sum2[n] - sum2[r] + sum1[r] - sum2[l - 1] + maxi);
    }
  }
  cout << ans;
  return 0;
}

```