object Main {
  def main(args: Array[String]): Unit = {
    val str = io.StdIn.readLine().split(' ').map(_.toInt)
    val a = str(0)
    val b = str(1)
    println(if ((a+b)>=10) "error"else (a+b).toString)
  }

  def judge(a: Int, b: Int): String = {
    if (a + b < 10) {
      (a + b).toString
    } else {
      "error"
    }
  }
}
