#include <bits/stdc++.h>
using namespace std;

int main()
{
	int n, m;
	cin >> n >> m;
	string s;
	for( int i = 0; i < n; i++ ) {
		string ss;
		cin >> ss;
		s += ss;
	}

	string ans = "NO";
	for( int i = 0; i < s.size() - 3; i++ ) {
		if( s[i] == 'L' && s[i + 1] == 'O' && s[i + 2] == 'V' && s[i + 3] == 'E' ) ans = "YES";
	}

	cout << ans << endl;
}