#include <bits/stdc++.h>
using namespace std;
int main() {
  char s[18];
  for (int i = 1; i <= 8; i++) {
    cin >> s;
    bool p = false;
    for (int j = 1; j < 8; j++)
      if (s[j] == s[j - 1]) {
        p = true;
        break;
      }
    if (p) {
      cout << "NO";
      return 0;
    }
  }
  cout << "YES";
  return 0;
}
