use proconio::input;

fn main(){
  input!{
    n: usize,
    a: [i32; n],
  }
  
  let mut ok = false;
  for i in 2..n{
    if a[i-2] == a[i]{
      ok = true;
    }
  }
  for i in 1..n{
    if a[i-1] == a[i]{
      ok = true;
    }
  }
  
  println!("{}", if ok{"Yes"} else{"No"});
}