#include <cstdio>
#include <cstring>
#include <iostream>
#include <string>
#include <cmath>
#include <bitset>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <deque>
#include <algorithm>

using namespace std;
typedef long long int ll;

int main()
{
	int n, m;
	scanf("%d %d", &n, &m);
	if(m<=3){
		printf("NO\n");
		return 0;
	}
	
	for(int i=0; i<n; i++){
		string s;
		cin>>s;
		for(int j=0; j<m-3; j++){
			if(s[j]=='L' && s[j+1]=='O' && s[j+2]=='V' && s[j+3]=='E'){
				printf("YES\n");
				return 0;
			}
		}
	}
	printf("NO\n");
	return 0;
}