fun main(args:Array<String>) {
  val n = readLine()!!.toInt()
  val ms = readLine()!!.split(" ").map(String::toInt)
  var targ = (1..n).toSet() - ms.toSet()
  val o = mutableMapOf<Int,Int>()
  ms.map { 
    if( o[it] == null ) o[it] = 0
    o[it] = o[it]!! + 1
  }  
  var o2 = o.toList().filter { it.second > 1 }.toMutableList()

  var result = 0
  while(true) {
    val p = o2.map {
      val (k,v) = it
      targ.map { ta -> 
        Triple(ta, k, Math.abs( ta - k ) )
      }
    }.flatten().minBy { it.third }!!
    //println( p ) 
    targ = targ.filter { it != p.first }.toMutableSet()
    o2 = o2.map { 
      val (k,v) = it
      if( k == p.second ) Pair(k, v-1)
      else Pair(k, v)
    }.filter { it.second > 1 } .toMutableList()
    //println(o2)
    result += p.third
    if( o2.size == 0 ) break
  }
  println(result)
}