#include <bits/stdc++.h>
using namespace std;
string s = "WBWBWBWB", t = "BWBWBWBW";
int main() {
  string f;
  for (int i = 0; i < 8; ++i) {
    cin >> f;
    bool b = f == s || f == t;
    if (!b) {
      cout << "NO" << endl;
      return 0;
    }
  }
  cout << "YES" << endl;
  return 0;
}
