#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, hash = 0;
  char s[100][100];
  cin >> n;
  for (int i = 0; i < n; i++)
    for (int j = 0; j < n; j++) {
      cin >> s[i][j];
      if (s[i][j] == '#') hash++;
    }
  for (int i = 0; i < n - 2; i++)
    for (int j = 0; j < n - 2; j++) {
      if (s[i][j + 1] == '#' && s[i + 1][j] == '#' && s[i + 1][j + 1] == '#' &&
          s[i + 1][j + 2] == '#' && s[i + 2][j + 1] == '#')
        s[i][j + 1] = s[i + 1][j] = s[i + 1][j + 1] = s[i + 1][j + 2] =
            s[i + 2][j + 1] = '.',
                 hash -= 5;
    }
  if (hash == 0)
    cout << "YES" << endl;
  else
    cout << "NO";
  return 0;
}
