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