#include "bits/stdc++.h"
using namespace std;
using Graph = vector<vector<int>>;
typedef long long ll;
typedef pair<ll, ll> P;
#define rep(i,n) for (ll i = 0; i < (n); ++i)
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
const long long mod = 1e9 + 7;

ll gcd(ll a, ll b) {
	return b ? gcd(b, a % b) : a;
}

ll lcm(ll a, ll b) {
	return a / gcd(a, b) * b;
}

int main() {
	ll n, m;
	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" << endl;
				return 0;
			}
		}
	}

	cout << "NO" << endl;
}