#include <bits/stdc++.h>
using namespace std;
char a[1000][1000];
bool u[1000][1000];
int n;
int main() {
  cin >> n;
  for (int i = 0; i < n; i++)
    for (int j = 0; j < n; j++) cin >> a[i][j];
  for (int i = 1; i < n - 1; i++) {
    for (int j = 1; j < n - 1; j++) {
      if (a[i][j] == '#' && a[i + 1][j] == '#' && a[i - 1][j] == '#' &&
          a[i][j + 1] == '#' && a[i][j - 1] == '#' && u[i][j] == 0 &&
          u[i + 1][j] == 0 && u[i - 1][j] == 0 && u[i][j + 1] == 0 &&
          u[i][j - 1] == 0) {
        u[i][j] = 1;
        u[i + 1][j] = 1;
        u[i - 1][j] = 1;
        u[i][j + 1] = 1;
        u[i][j - 1] = 1;
      }
    }
  }
  bool no = 0;
  for (int i = 0; i < n; i++)
    for (int j = 0; j < n; j++)
      if (!u[i][j] && a[i][j] == '#') no = 1;
  if (no)
    cout << "NO";
  else
    cout << "YES";
  return 0;
}
