#include <bits/stdc++.h>
using namespace std;
using i64=long long;
#define UNUSED -1
#define all(x) x.begin(),x.end()
#define pb push_back
const int mod=1e9+7,inf=1e9+1;
const int N=2e5;
mt19937 rng(69);
struct node
{
i64 key;
int pri,cnt;
i64 lazy;
node* l,* r;
node(int key)
{
this->key=key;
pri=rng();
cnt=1;
lazy=0;
l=r=nullptr;
}
void add(int x)
{
key+=x;
lazy+=x;
}
void push_down()
{
if(l!=nullptr)l->add(lazy);
if(r!=nullptr)r->add(lazy);
lazy=0;
}
};
int count(node* t)
{
if(t==nullptr)
{
return 0;
}
return t->cnt;
}
void recalc(node* t)
{
t->cnt=count(t->l)+count(t->r)+1;
}
void split(node* t,node*& l,node*& r,int cnt)
{
if(t==nullptr)
{
l=r=nullptr;
return;
}
t->push_down();
if(count(t->l)+1<=cnt)
{
split(t->r,t->r,r,cnt-count(t->l)-1);
l=t;
}
else
{
split(t->l,l,t->l,cnt);
r=t;
}
recalc(t);
}
void split_key(node* t,node*& l,node*& r,int key)
{
if(t==nullptr)
{
l=r=nullptr;
return;
}
t->push_down();
if(t->key<=key)
{
split_key(t->r,t->r,r,key);
l=t;
}
else
{
split_key(t->l,l,t->l,key);
r=t;
}
recalc(t);
}
void merge(node*& t,node* l,node* r)
{
if(l==nullptr)
{
t=r;
return;
}
if(r==nullptr)
{
t=l;
return;
}
l->push_down();
r->push_down();
if(l->pri >= r->pri)
{
merge(l->r,l->r,r);
t=l;
}
else
{
merge(r->l,l,r->l);
t=r;
}
recalc(t);
}
int leftest(node*& t)
{
if(t->l==nullptr)
{
return t->key;
}
t->push_down();
return leftest(t->l);
}
int rightest(node*& t)
{
if(t->r==nullptr)
{
return t->key;
}
t->push_down();
return rightest(t->r);
}
void print(node* t)
{
if(t==nullptr)
{
return;
}
t->push_down();
print(t->l);
cout<<t->key<<' ';
print(t->r);
}
int n,h;
int main()
{
ios::sync_with_stdio(false);
cin.tie(0);
cin>>n>>h;
node* root=nullptr;
i64 rez=0;
int last_l=0,last_r=0;
for(int i=1;i<=n;i++)
{
int x;
cin>>x;
if(i!=1)
{
rez+=max(last_l-x , 0);
rez+=max(x-last_r , 0);
}
node *l,*r;
split_key(root,l,r,x);
merge(l,l,new node(x));
merge(l,l,new node(x));
merge(root,l,r);
split(root,l,r,i);
assert(l!=nullptr);
assert(r!=nullptr);
l->add(-h);
r->add(h);
last_l=rightest(l),last_r=leftest(r);
merge(root,l,r);
}
cout<<rez;
}
