#include<bits/stdc++.h>
using namespace std;
int main(){
    int n,m;
    cin >> n >> m;
    string s;
    int ans=0;
    for(int i=0; i<n; i++){
        cin >> s;
        for(int i=0; i<m-3; i++){
            if(s[i]=='L'&&s[i+1]=='O'&&s[i+2]=='V'&&s[i+3]=='E') ans++;
        }
    }
    if(ans!=0) cout << "YES" << endl;
    else cout << "NO" << endl;
}