#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, i, j, s = 0, o;
  cin >> n;
  char *a[n + 1], str[n + 1];
  for (i = 0; i < n; i++) {
    cin >> str;
    a[i] = (char *)malloc(n + 1);
    strcpy(a[i], str);
  }
  for (i = 0; i < n && s == 0; i++)
    for (j = 0; j < n && s == 0; j++) {
      o = 0;
      if (j != 0 && a[i][j - 1] == 'o') o++;
      if ((j != n - 1) && a[i][j + 1] == 'o') o++;
      if (i != 0 && a[i - 1][j] == 'o') o++;
      if ((i != n - 1) && a[i + 1][j] == 'o') o++;
      if (o % 2 != 0) s = 1;
    }
  if (s)
    cout << "NO";
  else
    cout << "YES";
}
