#include <bits/stdc++.h>
#define rep(i,n)for(long long i=0;i<(n);i++)
using namespace std;
typedef long long ll;
const int MOD=1e9+7;
const int MAX = 1000000;
const int INF = 1e9;
const double pi=acos(-1);

int main(){
  int n,m;
  cin >> n >> m;
  vector<string>s(n);
  if(m<4){
    cout << "NO" << endl;
    return 0;
  }
  rep(i,n) cin >> s[i];
  rep(i,n){
    rep(j,m-3){
      if(s[i][j]=='L' && s[i][j+1]=='O' && s[i][j*2]=='V' && s[i][j+3]=='E'){
        cout <<"YES"<<endl;
        return 0;
      }
    }
  }
  cout <<"NO"<<endl;
  
  return 0;
}