object Main {
  import java.io.{BufferedReader, InputStream, InputStreamReader}
  import java.util.StringTokenizer
  import scala.reflect.ClassTag

  def main(args: Array[String]): Unit = {
    val out = new java.io.PrintWriter(System.out)
    new Main(out, new InputReader(System.in)).solve()
    out.flush()
  }

  private[this] val oj = System.getenv("MY_DEBUG") == null
  def DEBUG(f: => Unit): Unit = {
    if (!oj){ f }
  }
  def debug(as: Array[Boolean]): Unit = if (!oj){ debug(as.map(x => if(x) "1" else "0").mkString) }
  def debug(as: Array[Int]): Unit = if (!oj){ debug(as.mkString(" ")) }
  def debug(as: Array[Long]): Unit =if (!oj){ debug(as.mkString(" ")) }
  def debugDim(m: Array[Array[Int]]): Unit = if (!oj){
    REP(m.length) { i =>
      debug(m(i))
    }
  }
  def debugDimFlip(m: Array[Array[Long]]): Unit = if (!oj){
    REP(m(0).length) { j =>
      REP(m.length) { i =>
        System.err.print(m(i)(j))
        System.err.print(" ")
      }
      System.err.println()
    }
  }
  def debug(s: => String): Unit = {
    if (!oj){ System.err.println(s) }
  }
  def isDebug[A](debug: => A, online: => A): A = {
    if (oj) online else debug
  }

  class InputReader(val stream: InputStream) {
    private[this] val reader = new BufferedReader(new InputStreamReader(stream), 32768)
    private[this] var tokenizer: StringTokenizer = _

    private[this] def next(): String = {
      while (tokenizer == null || !tokenizer.hasMoreTokens)
        tokenizer = new StringTokenizer(reader.readLine)
      tokenizer.nextToken
    }

    def nextInt(): Int = Integer.parseInt(next())
    def nextLong(): Long = java.lang.Long.parseLong(next())
    def nextChar(): Char = next().charAt(0)

    def ni(): Int = nextInt()
    def nl(): Long = nextLong()
    def nc(): Char = nextChar()
    def ns(): String = next()
    def ns(n: Int): Array[Char] = ns().toCharArray
    def na(n: Int, offset: Int = 0): Array[Int] = map(n)(_ => ni() + offset)
    def na2(n: Int, offset: Int = 0): (Array[Int], Array[Int]) = {
      val A1, A2 = Array.ofDim[Int](n)
      REP(n) { i =>
        A1(i) = ni() + offset
        A2(i) = ni() + offset
      }
      (A1, A2)
    }
    def nm(n: Int, m: Int): Array[Array[Int]] = {
      val A = Array.ofDim[Int](n, m)
      REP(n) { i =>
        REP(m) { j =>
          A(i)(j) = ni()
        }
      }
      A
    }
    def nal(n: Int): Array[Long] = map(n)(_ => nl())
    def nm_c(n: Int, m: Int): Array[Array[Char]] = map(n) (_ => ns(m))
  }

  def REP(n: Int, offset: Int = 0)(f: Int => Unit): Unit = {
    var i = offset
    val N = n + offset
    while(i < N) { f(i); i += 1 }
  }
  def REP_r(n: Int, offset: Int = 0)(f: Int => Unit): Unit = {
    var i = n - 1 + offset
    while(i >= offset) { f(i); i -= 1 }
  }
  def TO(from: Int, to: Int)(f: Int => Unit): Unit = {
    REP(to - from + 1, from)(f)
  }
  def map[@specialized A: ClassTag](n: Int, offset: Int = 0)(f: Int => A): Array[A] = {
    val res = Array.ofDim[A](n)
    REP(n)(i => res(i) = f(i + offset))
    res
  }

  def sumL(as: Array[Int]): Long = {
    var s = 0L
    REP(as.length)(i => s += as(i))
    s
  }
  def cumSum(as: Array[Int]): Array[Long] = {
    val cum = Array.ofDim[Long](as.length + 1)
    REP(as.length) { i =>
      cum(i + 1) = cum(i) + as(i)
    }
    cum
  }
}

object Workspace {
  import Main._
  import java.util.Arrays.sort

  import scala.collection.mutable
  import math.{abs, max, min}
  import mutable.ArrayBuffer

  class BIT(n: Int, zero: Long)(f: (Long, Long) => Long) {
    def this(n: Int) = this(n, 0)(_ + _)

    private val N = {
      val a = Integer.highestOneBit(n)
      if (a == n) a else a << 1
    }
    private val bit = if (zero != 0) Array.fill[Long](N + 1)(zero) else Array.ofDim[Long](N + 1)

    /**
     * 1 index
     * addとindex違うよ
     * cumsumなんかといっしょ
     */
    def sum(i: Int): Long = {
      assert(i <= n)
      var x = i
      var s: Long = zero
      while(x > 0) {
        s = f(s, bit(x))
        x -= x & -x
      }
      s
    }

    /**
     * 0 index
     */
    def add(i: Int, a: Long): Unit = {
      assert(i < n)
      var x = i + 1
      while(x <= N) {
        bit(x) = f(bit(x), a)
        x += x & -x
      }
    }

    def sumAll: Long = sum(n)

    // A がLongとかじゃない場合はこれらを実装しないと下の奴らが使えない
    private def sub(a: Long, b: Long) = a - b
    private def lt(a: Long, b: Long) = a < b

    /**
     * [l, r)
     */
    def query(l: Int, r: Int): Long = {
      assert(r > l)
      sub(sum(r), sum(l))
    }

    def lowerBound(W: Long): Int = {
      var k = N
      var x = 0
      var w = W
      while(k > 0) {
        if (x + k <= N && lt(bit(x + k), w)) {
          w = sub(w, bit(x + k))
          x += k
        }
        k /= 2
      }
      math.min(n, x)
    }
  }
}

class Main(out: java.io.PrintWriter, sc: Main.InputReader) {
  import sc._
  import Main._
  import java.util.Arrays.sort

  import scala.collection.mutable
  import math.{abs, max, min}
  import mutable.ArrayBuffer
  import Workspace._

  // toIntとか+7とかするならvalにしろ
  final private[this] val MOD = 1000000007

  def solve(): Unit = {
    val N, M = ni()
    val A = na(N, -1)
    val c0 = new BIT(M + 1)
    val c1 = new BIT(M + 1)
    var sum = 0L
    REP(N - 1) { i =>
      val diff = (M + A(i + 1) - A(i)) % M
      sum += diff
      if (diff > 1) {
        val s = (A(i) + 1) % M
        val t = A(i + 1)
        debug(s"i:$i diff:$diff s:$s t$t")
        if (s < t) {
          c1.add(s, 1)
          c1.add(t + 1, -1)
          c0.add(s, -s)
          c0.add(t + 1, s)
        } else {
          c1.add(s, 1)
          c1.add(M, -1)
          c0.add(s, -s)
          c0.add(M, s)

          c1.add(0, 1)
          c1.add(t + 1, -1)
          c0.add(0, M - s)
          c0.add(t + 1, -(M - s))
        }
      }
    }
    var reduce = 0L
    REP(M) { i =>
      val v = c0.sum(i + 1) + c1.sum(i + 1) * i
//      debug(s"$i ${c0.sum(i + 1)} ${c1.sum(i + 1)}")
      debug(s"i:$i v:$v")
      reduce = max(reduce, v)
    }
    out.println(sum - reduce)
  }
}

Measured memory_bytes: 42124