#include <bits/stdc++.h>

using namespace std;

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