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