#include <iostream>
#include <string>
using namespace std;

int main() {
    int n, m;
    cin >> n >> m;
    if (m < 4) {
        cout << "NO" << endl;
        return 0;
    }
    while (n--){
        string s;
        cin >> s;
        for (int i = 0; i + 3 < m; ++i){
            if (s[i] == 'L' and s[i + 1] == 'O' and s[i + 2] == 'V' and s[i + 3] == 'E'){
                cout << "YES" << endl;
                return 0;
            }
        }
    }
    cout << "NO" << endl;
    return 0;
}