#include <bits/stdc++.h>
using namespace std;
inline int in() {
  int x = 0;
  bool f = 0;
  char c;
  for (; (c = getchar()) < '0' || c > '9'; f = c == '-')
    ;
  for (x = c - '0'; (c = getchar()) >= '0' && c <= '9';
       x = (x << 3) + (x << 1) + c - '0')
    ;
  return f ? -x : x;
}
int sum1[2005], sum2[2005], res[2005], a[2005];
int n, ml, mr, mx;
int main() {
  n = in();
  mx = 0;
  for (int i = 1; i <= n; ++i) {
    a[i] = in();
    sum1[i] = sum1[i - 1] + (a[i] == 1);
    sum2[i] = sum2[i - 1] + (a[i] == 2);
  }
  for (int i = 1; i <= n; ++i) {
    ml = mr = 0;
    res[i] = sum1[i] + sum2[n] - sum2[i];
    for (int l = 1; l <= i; ++l)
      ml = max(ml, sum1[l - 1] + sum2[i] - sum2[l - 1]);
    for (int r = i + 1; r <= n; ++r)
      mr = max(mr, sum1[r] - sum1[i] + sum2[n] - sum2[r]);
    res[i] = max(res[i], ml + mr);
  }
  for (int i = 1; i <= n; ++i) mx = max(mx, res[i]);
  printf("%d", mx);
  return 0;
}

### Prompt

Generate a CPP solution 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;
inline int in() {
  int x = 0;
  bool f = 0;
  char c;
  for (; (c = getchar()) < '0' || c > '9'; f = c == '-')
    ;
  for (x = c - '0'; (c = getchar()) >= '0' && c <= '9';
       x = (x << 3) + (x << 1) + c - '0')
    ;
  return f ? -x : x;
}
int sum1[2005], sum2[2005], res[2005], a[2005];
int n, ml, mr, mx;
int main() {
  n = in();
  mx = 0;
  for (int i = 1; i <= n; ++i) {
    a[i] = in();
    sum1[i] = sum1[i - 1] + (a[i] == 1);
    sum2[i] = sum2[i - 1] + (a[i] == 2);
  }
  for (int i = 1; i <= n; ++i) {
    ml = mr = 0;
    res[i] = sum1[i] + sum2[n] - sum2[i];
    for (int l = 1; l <= i; ++l)
      ml = max(ml, sum1[l - 1] + sum2[i] - sum2[l - 1]);
    for (int r = i + 1; r <= n; ++r)
      mr = max(mr, sum1[r] - sum1[i] + sum2[n] - sum2[r]);
    res[i] = max(res[i], ml + mr);
  }
  for (int i = 1; i <= n; ++i) mx = max(mx, res[i]);
  printf("%d", mx);
  return 0;
}

```