import java.util.Scanner
object Main {
val d: List[Int] = List(2, 3, 5, 7, 11, 13)
val e: List[Int] = List(4, 6, 8, 9, 10, 12)
val sc = new Scanner(System.in)
def main(args: Array[String]): Unit = {
val n = sc.nextInt()
val t = sc.nextInt()
println(solve(n, t, 0))
}
def solve(n: Int, t: Int, close_time: Int): Int = {
if(n == 0){
0
}else{
val a = sc.nextInt()
Math.min(t, a + t - close_time) + solve(n-1, t, a + t)
}
}
/**
* P16
*/
def drop[T](n: Int, list: List[T]): List[T] = {
def f(i: Int)(n: Int, list: List[T]): List[T] = (i, n, list) match {
case (_, _, Nil) => Nil
case (1, n, car :: cdr) => f(n)(n, cdr)
case (i, n, car :: cdr) => car :: f(i-1)(n, cdr)
}
f(n)(n, list)
}
/*
def d[T](i: Int, n: Int, list: List[T]): List[T] = (i, n, list) match {
case (_, _, Nil) => Nil
case (1, n, car :: cdr) => d(n, n, cdr)
case (i, n, car :: cdr) => car :: d(i-1, n, cdr)
}
*/
/**
* P12
*/
/*
def decode[T](list: List[List[T]]): List[T] = list match {
case Nil => Nil
case List(n, v) :: cdr =>
for(i <- 1 to n) yield {v} :: cdr
}
*/
/**
* P11
*/
def encode[T](list: List[T]): List[(Int, T)] = list match {
case Nil => Nil
case car :: cdr => {
val (first, second) = list.span(x => x == car)
(first.length, car) :: encode(second)
}
}
/**
* P10
*/
def encodeModified[T](list: List[T]): List[Any] = list match {
case Nil => Nil
case first :: second :: cdr if first != second =>
first :: encodeModified(second :: cdr)
case car :: cdr => {
val (first, second) = list.span(x => x == car)
(first.length, car) :: encodeModified(second)
}
}
/**
* P09
*/
def pack[T](list: List[T]): List[List[T]] = list match {
case Nil => Nil
case car :: cdr => {
val (first, second) = list.span(x => x == car)
first :: pack(second)
}
}
/**
* P08
*/
def compress[T](list: List[T]): List[T] = list match {
case first :: second :: cdr if first == second => compress(first :: cdr)
case car :: cdr => car :: compress(cdr)
case Nil => Nil
}
/**
* P07
*/
def flatten(list: List[Any]): List[Any] = list.flatMap {
case l: List[_] => flatten(l)
case elm => List(elm)
}
/**
* P06
*/
def isParindrome[T](list: List[T]): Boolean = list == list.reverse
/**
* P05
*/
def reverse[T](list: List[T]): List[T] =
list.foldLeft(List.empty[T])((x, y) => y :: x)
/**
* P04
*/
def length[T](list: List[T]): Int = list match {
case Nil => 0;
case car :: cdr => 1 + length(cdr)
}
/**
* P03
*/
def nth[T](n: Int, list: List[T]): T = (n, list) match {
case (0, car :: cdr) => car
case (m, car :: cdr) => nth(m-1, cdr)
case _ => throw new Exception
}
/**
* P02
*/
def penultimate[T](list: List[T]): T = list match {
case first :: second :: Nil => first
case car :: cdr => last(cdr)
case _ => throw new Exception
}
/**
* P01
*/
def last[T](list: List[T]): T = list match {
case car :: Nil => car
case car :: cdr => last(cdr)
case _ => throw new Exception
}
}