#include <bits/stdc++.h>
#define ll long long
using namespace std;
const int N = 5e4 + 10;
const int B = 12000;
const int M = 30000;
const int mod = 2999997;
const int W = 3000000;

mt19937 rnd(time(0));
int key = rnd() % mod;
struct Hash {
	struct node {
		int x, y;
		ll val;
		node(int a = 0, int b = 0, ll c = 0) {x = a; y = b; val = c;}
	}q[M];
	struct edge {
		int to, nxt;
	}e[M];
	int link[W], tot, cnt, num;
	
	int f(int x, int y) {
		x = (x ^ key) % mod; y = 1ll * (y + key) * key % mod;
		return 1ll * (3ll * x % mod * key) % mod * (y ^ (7ll * key % mod)) % mod + 1;
	}
	
	void ins(int x, int y, ll val) {
		int id = f(x, y);
		for (int i = link[id]; i; i = e[i].nxt) {
			int to = e[i].to;
			if (q[to].x == x && q[to].y == y) return q[to].val = min(q[to].val, val), void();
		}
		q[++cnt] = node(x, y, val);
		e[++tot].nxt = link[id]; e[tot].to = cnt; link[id] = tot;
	}
	
	void init() {
		for (int i = 1; i <= cnt; ++i) link[f(q[i].x, q[i].y)] = 0;
		tot = 0; num = cnt; cnt = 0;
		if (num <= B) return;
		nth_element(q + 1, q + 1 + B, q + 1 + num, [&](node xx, node yy) {return xx.val < yy.val;});
		num = B;
	}
}H[2];
int n, L, cnt, opt;

int main() {
	scanf("%d%d", &n, &L);
	H[opt].ins(0, 0, 0);
	for (int i = 1; i <= n; ++i) {
		int p, x, y; ll val;
		scanf("%d", &p); H[opt].init();
		for (int j = 1; j <= H[opt].num; ++j) {
			x = H[opt].q[j].x;
			y = H[opt].q[j].y;
			val = H[opt].q[j].val;
			if ((x <= p && p <= x + L) || (y <= p && p <= y + L)) H[opt ^ 1].ins(x, y, val);
			else if (p < x) H[opt ^ 1].ins(p, y, val + x - p);
			else if (y + L < p) H[opt ^ 1].ins(x, p - L, val + p - y - L);
			else {
				H[opt ^ 1].ins(p - L, y, val + p - x - L);
				H[opt ^ 1].ins(x, p, val + y - p);
			}
		}
		opt ^= 1;
	}
	ll ans = 1e18;
	for (int i = 1; i <= H[opt].cnt; ++i) ans = min(ans, H[opt].q[i].val);
	return printf("%lld\n", ans), 0;
}