#include<deque>
#include<queue>
#include<vector>
#include<algorithm>
#include<iostream>
#include<set>
#include<cmath>
#include<tuple>
#include<string>
#include<chrono>
#include<functional>
#include<iterator>
#include<random>
#include<unordered_set>
#include<unordered_map>
#include<array>
#include<map>
#include<iomanip>
using namespace std;
typedef long long int llint;
typedef long double lldo;
#define mp make_pair
#define mt make_tuple
#define pub push_back
#define puf push_front
#define pob pop_back
#define pof pop_front
#define fir first
#define sec second
#define res resize
#define ins insert
#define era erase
#define dme cout<<-1<<endl;return 0
//ios::sync_with_stdio(false);
//std::cin.tie(0);
//<< setprecision(20)
const int mod=1e9+7;
const llint big=1e16+100;
const long double pai=3.141592653589793238462643383279502884197;
const long double ena=2.71828182845904523536;
const long double eps=1e-7;
template <class T,class U>void mineq(T& a,U b){if(a>b){a=b;}}
template <class T,class U>void maxeq(T& a,U b){if(a<b){a=b;}}
llint gcd(llint a,llint b){if(a%b==0){return b;}else return gcd(b,a%b);}
llint lcm(llint a,llint b){return a/gcd(a,b)*b;}
int main(void){
	llint n,P;cin>>n>>P;
	llint dans=0,uans=big;
	llint mae;cin>>mae;n--;
	//uans <<<<
	//dans >>>>
	while(n--){
		llint h;cin>>h;
		llint md=dans,mu=uans;
		dans=md+max(0LL,h-mae);
		uans=mu+max(0LL,mae-h);
		mineq(dans,mu+P);
		mineq(uans,md+P);
		//cout<<"de"<<dans<<" "<<uans<<endl;
		mae=h;
	}
	cout<<min(uans,dans)<<endl;
	return 0;
}