#include<iostream>
#include<algorithm>
#include <vector>
#include<cmath>
using namespace std;
int main() {
	int n, m;
	cin >> n >> m;
	if (m < 4) {
		cout << "NO" << endl;
	}
	else {
		vector<string>vec(n);
		for (int ia = 0; ia < n; ia++) {
			cin >> vec.at(ia);
		}
		int cnt = 0;
		for (int ib = 0; ib < n; ib++) {
			for (int ic = 0; ic < m - 4; ic++) {
				if (vec.at(ib).at(ic) == 'L' && vec.at(ib).at(ic + 1) == 'O' && vec.at(ib).at(ic + 2) == 'V' && vec.at(ib).at(ic + 3) == 'E') {
					cnt++;
				}
			}
		}
		if (cnt) {
			cout << "YES" << endl;
		}
		if (!cnt) {
			cout << "NO" << endl;
		}
	}
}