#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
using namespace std;
template <typename T, typename TT>
inline ostream &operator<<(ostream &os, const pair<T, TT> &t) {
  return os << t.first << " " << t.second;
}
template <typename T>
inline ostream &operator<<(ostream &os, const vector<T> &t) {
  for (auto i : t) os << i << " ";
  return os;
}
template <typename T>
inline istream &operator>>(istream &is, vector<T> &v) {
  for (T &t : v) is >> t;
  return is;
}
template <typename T1, typename T2>
inline istream &operator>>(istream &is, pair<T1, T2> &t) {
  is >> t.first >> t.second;
  return is;
}
const long long mod = 1e9 + 7;
void solve() {
  int n;
  cin >> n;
  vector<string> s(n);
  vector<long long> col(n), row(n);
  cin >> s;
  long long ans = 0;
  for (int i = 0; i < n; i++) {
    int j, use = 0;
    for (j = n - 1; j > i; j--) {
      int cur = s[i][j] - '0' + use + col[j];
      if (cur & 1) {
        use++;
        ans++;
        col[j]++;
      }
    }
    int use1 = 0;
    for (j = n - 1; j > i; j--) {
      int cur = s[j][i] - '0' + row[j] + use1;
      if (cur & 1) {
        use1++;
        ans++;
        row[j]++;
      }
    }
    ans += (use + use1 + s[i][i] - '0' + row[i] + col[i]) % 2;
  }
  cout << ans << '\n';
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  ;
  int T = 1;
  while (T--) {
    solve();
  }
  return 0;
}
