#include <bits/stdc++.h>
using namespace std;
void solve();
int32_t main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  ;
  int t = 1;
  for (int i = 1; i <= t; ++i) solve();
  cerr << "Time taken: " << ((clock() * 1000) / CLOCKS_PER_SEC) << "ms\n";
}
void solve() {
  int n;
  cin >> n;
  char arr[n][n];
  for (int i = 0; i < n; ++i) {
    for (int j = 0; j < n; ++j) {
      cin >> arr[i][j];
    }
  }
  int vis[n][n];
  memset(vis, 0, sizeof(vis));
  for (int i = 0; i < n; ++i) {
    for (int j = 0; j < n; ++j) {
      if (arr[i][j] == '.' or vis[i][j]) continue;
      if (j - 1 >= 0 and j + 1 < n and i + 2 < n) {
        if (arr[i + 1][j - 1] == '#' and arr[i + 1][j + 1] == '#' and
            arr[i + 1][j] == '#' and arr[i + 2][j] == '#') {
          if (vis[i + 1][j - 1] == 1 or vis[i + 1][j + 1] == 1 or
              vis[i + 1][j] == 1 or vis[i + 2][j] == 1) {
            cout << "NO" << '\n';
            return;
          }
          vis[i + 1][j - 1] = 1;
          vis[i + 1][j + 1] = 1;
          vis[i + 1][j] = 1;
          vis[i + 2][j] = 1;
          vis[i][j] = 1;
        } else {
          cout << "NO" << '\n';
          return;
        }
      } else {
        cout << "NO" << '\n';
        return;
      }
    }
  }
  cout << "YES" << '\n';
}
