#include <bits/stdc++.h>
using namespace std;
int nonDecStart[2003];
int nonDecEnd[2003];
int nonIncEnd[2003];
int nonIncStart[2003];
int arr[2003];
int mat[2003][2003];
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int n;
  cin >> n;
  for (int i = 0; i < n; i++) {
    mat[i][i] = 1;
    cin >> arr[i];
  }
  for (int i = 0; i < n; i++) {
    int twos = 0;
    if (arr[i] == 2) twos++;
    for (int j = i + 1; j < n; j++) {
      if (arr[j] == 2) {
        twos++;
        mat[i][j] = max(twos, mat[i][j - 1]);
      } else
        mat[i][j] = mat[i][j - 1] + 1;
    }
  }
  for (int i = 0; i < n; i++) {
    nonDecEnd[i] = 1;
    nonIncEnd[i] = 1;
    for (int j = i - 1; j >= 0; j--) {
      if (arr[j] <= arr[i]) {
        nonDecEnd[i] = max(nonDecEnd[i], nonDecEnd[j] + 1);
      }
      if (arr[j] >= arr[i]) nonIncEnd[i] = max(nonIncEnd[i], nonIncEnd[j] + 1);
    }
  }
  for (int i = n - 1; i >= 0; i--) {
    nonDecStart[i] = 1;
    nonIncStart[i] = 1;
    for (int j = i + 1; j < n; j++) {
      if (arr[j] >= arr[i])
        nonDecStart[i] = max(nonDecStart[i], nonDecStart[j] + 1);
      if (arr[j] <= arr[i])
        nonIncStart[i] = max(nonIncStart[i], nonIncStart[j] + 1);
    }
  }
  int best = nonDecStart[0];
  for (int l = 0; l < n; l++) {
    for (int r = l + 1; r < n; r++) {
      int temp = 0;
      if (l > 0) temp += nonDecEnd[l - 1];
      if (r < n - 1) temp += nonDecStart[r + 1];
      temp += mat[l][r];
      if (temp > best) best = temp;
    }
  }
  cout << best << endl;
  return 0;
}
