#include <bits/stdc++.h>
using namespace std;
const int N = 2005;
int n, a[N], s1[N], s2[N], ans = 0;
void judge(int x, int y, int mid) {
  int tmp = 0;
  if (x == y)
    tmp = s1[mid] + s2[n] - s2[mid];
  else
    tmp = s1[x - 1] + s2[n] - s2[y] + s2[mid] - s2[x - 1] + s1[y] - s1[mid];
  ans = max(ans, tmp);
}
int main() {
  scanf("%d", &n);
  int i, j, x, y;
  for (i = 1; i <= n; i++) scanf("%d", &a[i]);
  for (i = 1; i <= n; i++) {
    s1[i] = s1[i - 1];
    s2[i] = s2[i - 1];
    if (a[i] == 1)
      s1[i]++;
    else
      s2[i]++;
  }
  int mx, val, mid;
  for (x = 1; x <= n; x++) {
    if (a[x] == 1)
      val = -1;
    else
      val = 1;
    mid = x;
    mx = val;
    judge(x, x, x);
    judge(x, x, x - 1);
    for (y = x + 1; y <= n; y++) {
      if (a[y] == 1)
        val--;
      else
        val++;
      if (val > mx) mx = val, mid = y;
      judge(x, y, mid);
    }
  }
  printf("%d", ans);
  return 0;
}

### Prompt

Create a solution in Cpp for 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 int N = 2005;
int n, a[N], s1[N], s2[N], ans = 0;
void judge(int x, int y, int mid) {
  int tmp = 0;
  if (x == y)
    tmp = s1[mid] + s2[n] - s2[mid];
  else
    tmp = s1[x - 1] + s2[n] - s2[y] + s2[mid] - s2[x - 1] + s1[y] - s1[mid];
  ans = max(ans, tmp);
}
int main() {
  scanf("%d", &n);
  int i, j, x, y;
  for (i = 1; i <= n; i++) scanf("%d", &a[i]);
  for (i = 1; i <= n; i++) {
    s1[i] = s1[i - 1];
    s2[i] = s2[i - 1];
    if (a[i] == 1)
      s1[i]++;
    else
      s2[i]++;
  }
  int mx, val, mid;
  for (x = 1; x <= n; x++) {
    if (a[x] == 1)
      val = -1;
    else
      val = 1;
    mid = x;
    mx = val;
    judge(x, x, x);
    judge(x, x, x - 1);
    for (y = x + 1; y <= n; y++) {
      if (a[y] == 1)
        val--;
      else
        val++;
      if (val > mx) mx = val, mid = y;
      judge(x, y, mid);
    }
  }
  printf("%d", ans);
  return 0;
}

```