/*
 * Solution Template for Off the Track
 * 
 * Australian Informatics Olympiad 2025
 * 
 * This file is provided to assist with reading of input and writing of output
 * for the problem. You may modify this file however you wish, or
 * you may choose not to use this file at all.
 */

#include <cstdio>

/* N is the number of students. */
int N;
/* L is the length of the track. */
int L;

/*
 * P contains the locations of the students. Note that the array starts from 0,
 * and so the values are P[0] to P[N-1].
 */
int P[200005];

int answer;
int main(void) {
  /* Read the values of N, L, and the student locations. */
  scanf("%d%d", &N, &L);
  for (int i = 0; i < N; i++) {
    scanf("%d", &P[i]);
  }

  /*
   * TODO: This is where you should compute your solution. Store the fewest
   * number of seconds you need to end the game into the variable answer.
   */

  /* Write the answer. */
  printf("%d\n", answer);

  return 0;
}