#include <bits/stdc++.h>
using namespace std;
int main() {
  char a, b;
  for (int i = 0; i < 8; i++) {
    cin >> a;
    for (int j = 0; j < 7; j++) {
      b = a;
      cin >> a;
      if (a == b) {
        cout << "NO";
        return 0;
      }
    }
  }
  cout << "YES";
  return 0;
}
