#include <bits/stdc++.h>
using namespace std;
const int inf = (int)1e9 + 7;
const int N = (int)1e5 + 4;
const int M = 1001;
char a[M][M];
bool u[M][M];
int main() {
  int n;
  cin >> n;
  for (int i = 0; i < n; ++i) {
    for (int j = 0; j < n; ++j) {
      cin >> a[i][j];
    }
  }
  for (int i = 0; i < n; ++i) {
    for (int j = 0; j < n; ++j) {
      if (!u[i][j] && a[i][j] == '#') {
        if (i < n - 2 && j > 0 && j < n - 1 && a[i + 1][j - 1] == '#' &&
            a[i + 1][j] == '#' && a[i + 1][j + 1] == '#' &&
            a[i + 2][j] == '#' && !u[i + 1][j] && !u[i + 2][j] &&
            !u[i + 1][j - 1] && !u[i + 1][j + 1]) {
          u[i][j] = u[i + 1][j - 1] = u[i + 1][j] = u[i + 1][j + 1] =
              u[i + 2][j] = 1;
        } else {
          cout << "NO";
          return 0;
        }
      }
    }
  }
  cout << "YES";
  return 0;
}
