import scala.io.StdIn.{readInt,readLine}
  
object Main extends App {
  type Set = String => Boolean

  def contains(s:Set, elem:String):Boolean = s(elem)
  def singletonSet(elem:String):Set = x => x==elem
  def union(s:Set, t:Set):Set = x => contains(s,x) || contains(t,x)

  val n = readInt

  def loop(i:Int, s:Set, str:String):String =
    if(i>n) str.dropRight(1)
    else {
      val l = readLine.split(" ")
      if(l(0)(0)=='i') loop(i+1, union(singletonSet(l(1)),s),str)
      else if(contains(s,l(1))) loop(i+1, s, str+"yes\n")
      else loop(i+1, s, str+"no\n")
    }
  val l = readLine.split(" ")
  println(loop(2, singletonSet(l(1)),""))
}