#include <bits/stdc++.h>
using namespace std;
int n;
bool check(vector<vector<char>>& v, int x, int y) {
  if (x + 2 >= 0 && y - 1 >= 0 && y + 1 < n && v[x + 1][y] == '#' &&
      v[x + 2][y] == '#' && v[x + 1][y + 1] == '#' && v[x + 1][y - 1] == '#') {
    v[x][y] = v[x + 1][y] = v[x + 2][y] = v[x + 1][y + 1] = v[x + 1][y - 1] =
        '.';
    return true;
  }
  if (y + 2 < n && x - 1 >= 0 && x + 1 < n && v[x][y + 1] == '#' &&
      v[x][y + 2] == '#' && v[x - 1][y + 1] == '#' && v[x + 1][y + 1] == '#') {
    v[x][y] = v[x][y + 1] = v[x][y + 2] = v[x - 1][y + 1] = v[x + 1][y + 1] =
        '.';
    return true;
  }
  return false;
}
void print(vector<vector<char>> v) {
  for (int i = 0; i < n; i++) {
    for (int j = 0; j < n; j++) {
      cout << v[i][j];
    }
    cout << endl;
  }
}
int main() {
  cin >> n;
  vector<vector<char>> v(n, vector<char>(n));
  for (int i = 0; i < n; i++) {
    for (int j = 0; j < n; j++) {
      cin >> v[i][j];
    }
  }
  if (v[0][0] == '#' || v[n - 1][0] == '#' || v[0][n - 1] == '#' ||
      v[n - 1][n - 1] == '#') {
    cout << "NO";
    return 0;
  }
  int x, y;
  for (int i = 0; i < n; i++) {
    for (int j = 0; j < n; j++) {
      if (v[i][j] == '#') {
        if (!check(v, i, j)) {
          cout << "NO";
          return 0;
        }
      }
    }
  }
  cout << "YES";
}
