#include <bits/stdc++.h>

using namespace std;

int main() {
    int n, m;
    cin >> n >> m;

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