#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, i;
  string x;
  for (i = 1; i <= 8; i++) {
    cin >> x;
    if (x != "BWBWBWBW" && x != "WBWBWBWB") i = 10;
  }
  if (i == 9)
    cout << "YES\n";
  else
    cout << "NO\n";
}
