#include <iostream>
#include <list>
#include <vector>
#include <string>
#include <stdio.h>
#include <stdint.h>
#include <iomanip>
using namespace std;

using uint = unsigned int;
using ll = long long;

#define CIN( LL , A ) LL A; cin >> A 
#define GETLINE( A ) string A; getline( cin , A ) 
#define FOR_ITR( ARRAY , ITR , END ) for( auto ITR = ARRAY .begin() , END = ARRAY .end() ; ITR != END ; ITR ++ ) 

int main()
{

  CIN( ll , n );
  CIN( ll , m );
  string S;
  const string L = "L";
  const string O = "O";
  const string V = "V";
  const string E = "E";
  ll state = -1;
  
  for( ll i = 0 ; i < n ; i++ ){

    state = -1;
    cin >> S;

    for( ll j = 0 ; j < m ; j++ ){

      const string c = S.substr( j , 1 );

      if( c == L ){

	state = 0;

      } else if( c == O ){

	state = ( state == 0 ? 1 : -1 );

      } else if( c == V ){

	state = ( state == 1 ? 2 : -1 );

      } else if( c == E ){

	if( state == 2 ){

	  cout << "YES" << endl;
	  return 0;

	}

	state = -1;

      } else {

	state = -1;

      }

    }

  }
  
  cout << "NO" << endl;
  return 0;

}