#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <numeric>

using namespace std;

#define REP(i,n)	for(int i=0;i<(n);++i)
#define REPS(i,s,t)	for(int i=(s);i<(t);++i)

#define INF 		2000000007
#define MOD			1000000007
#define MAX 		100005


typedef unsigned int 			uint;
typedef unsigned long long int	ull;
typedef long long int ll;

//uint dp[MAX];

int main(){
	int N,M;cin>>N>>M;
	bool flag = false;
	REP(i,N){
		string str;cin>>str;
		REP(j,M-4){
			if(str[j]=='L'&&str[j+1]=='O'&&str[j+2]=='V'&&str[j+3]=='E'){
				flag = true;
				break;
			}
		}
	}
	cout << (flag ? "YES" : "NO") << endl;


	return 0;
}