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