#include<iostream>
#include<cmath>
using namespace std;
int main(){
	string str;
	int n,m;
	cin >> n >> m;
	for(int i=0;i<n;i++){
			cin >> str;
			for(int i=0;i<int(str.size())-3;i++){
				if(str[i]=='L'&&str[i+1]=='O'&&str[i+2]=='V'&&str[i+3]=='E'){
					cout << "YES\n";
					return 0;
				}
			}
	}
	cout << "NO\n";
	return 0;
}