#include<bits/stdc++.h>

#define INF 1000000007
#define LINF 1000000000000000007

using namespace std;

typedef long long ll;
typedef pair<ll, ll> P;

int n, m;
string s[50];

int main(){
	cin >> n >> m;
	for(int i  =0; i < n; i++) cin >> s[i];
	
	int b = 0;
	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;
				b = 1;
			}
			if(b) break;
		}
		if(b) break;
	}
	if(!b) cout << "NO" << endl;
	
	return 0;
}