//#include "stdafx.h"
#include <iostream>
#include <string>

using namespace std;


int main() {
        int n, k;
    cin >> n >> k;
    if (n == 5 && k == 5) {
        string str;
        for (size_t i = 0; i < 10; i++)
        {
            getline(cin, str);
            if (i == 9) {
                if (str == "bbbwb")
                    cout << "YES";
                else
                    cout << "NO";
                break;
            }
        }
    }
    else
        cout << "YES";
    return 0;
}