#include <bits/stdc++.h>
using namespace std;
const int N = 100005, mod = 1000000007;
int n, m, T, q, f[6];
int main() {
  cin >> n;
  for (int i = 1; i <= n; i++) {
    int x;
    scanf("%d", &x);
    for (int j = 1; j <= 4; j++) {
      if ((j & 1) == (x & 1)) f[j]++;
    }
    for (int j = 2; j <= 4; j++) f[j] = max(f[j], f[j - 1]);
  }
  printf("%d\n", f[4]);
  return 0;
}
