#include <bits/stdc++.h>
using namespace std;
int dp[2][2005];
int a[2005];
int cnt2[2005];
int main() {
  int n;
  cin >> n;
  for (int i = 1; i <= n; i++) cin >> a[i];
  for (int i = n; i >= 1; i--) {
    cnt2[i] = cnt2[i + 1];
    if (a[i] == 2) cnt2[i]++;
  }
  for (int i = 0; i <= 2; i++) dp[i][0] = 1;
  for (int i = 1; i <= n; i++) {
    dp[0][i] = dp[1][i] = 1;
    for (int j = 1; j <= i - 1; j++) {
      if (a[i] >= a[j]) dp[0][i] = max(dp[0][j] + 1, dp[0][i]);
      if (a[i] <= a[j]) dp[1][i] = max(max(dp[0][j], dp[1][j]) + 1, dp[1][i]);
    }
  }
  int ans = 0;
  for (int i = 1; i <= n; i++) {
    ans = max(dp[1][i] + cnt2[i + 1], ans);
  }
  cout << ans << endl;
  return 0;
}
