fun main() {
    readLine()
    val a = readLine()!!.split(" ").map { it.toInt() }

    val result = a
        .sorted()
        .filterIndexed { index, value ->
            val beforeValue = a.getOrNull(index - 1)

            if (beforeValue == null) true else {
                (value - beforeValue != 1)
            }
        }
        .sum()
    println(result)
}