#include <bits/stdc++.h>
using namespace std;
int main() {
  vector<string> S(3);
  for (int i = 0; i < 3; i++) {
    cin >> S[i];
  }
  char idx = S[0][0];
  bool ok = true;
  for (int i = 0; i < 3; i++) {
    for (int j = 0; j < 3; j++) {
      if ((i + j) % 2 == 0) {
        if (S[i][j] != idx) {
          ok = false;
        }
      } else {
        if (S[i][j] == idx) {
          ok = false;
        }
      }
    }
  }
  if (ok) {
    cout << "Yes" << endl;
  } else {
    cout << "No" << endl;
  }
}