#include<bits/stdc++.h>
#define rep(i, x) for(ll i = 0; i < x; i++)
#define rep2(i, x) for(ll i = 1; i <= x; i++)
#define all(a) (a).begin(),(a).end()
using ll = long long;
using ld = long double;
const ll INF = 10000000000000000;
using namespace std;
signed main() {
    ll n, m, ans = 0; cin >> n >> m;
	rep(i, n) {
		string s; cin >> s;
		rep(j, m - 3) {
			if (s[j] == 'L' && s[j + 1] == 'O' && s[j + 2] == 'V' && s[j + 3] == 'E') { cout << "YES\n"; return 0; }
		}
	}
	cout << "NO" << endl;
	return 0;
}