#include <iostream>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <algorithm>
#include <string>
#include <vector>
using namespace std;
typedef long long ll;
int ans=0;
void aout(void){
	cout<<ans<<endl;
}
void out(int a){
	cout<<a<<endl;
}
int main(void){
	int m,n;
	cin>>m>>n;
	string s[n];
	for(int i=0;i<n;i++)cin>>s[i];
	for(int i=0;i<m;i++){
		for(int j=0;j<n-3;j++){
			if(s[i][j]=='L'&&s[i][j+1]=='O'&&s[i][j+2]=='V'&&s[i][j+3]=='E'){
				cout<<"YES\n";
				return 0;
			}
		}
	}
	cout<<"NO\n";
	return 0;
}