use std::io;

fn main() {
  let mut buf = String::new();
  io::stdin().read_line(&mut buf).ok();
  let l: Vec<u16> = buf
    .trim()
    .split_whitespace()
    .map(|e| e.parse().ok().unwrap())
    .collect();

  let mut found = false;
  for _i in 0..l[0] {
    let mut buf = String::new();
    io::stdin().read_line(&mut buf).ok();
    found = buf
      .trim()
      .chars()
      .collect::<Vec<char>>()
      .windows(4)
      .any(|c| match c {
        ['L', 'O', 'V', 'E'] => true,
        _ => false,
      });
    if found {
      break;
    }
  }

  if found {
    println!("YES")
  } else {
    println!("NO")
  }
}