#include<bits/stdc++.h>
using namespace std;
#define rep(i,n) for(ll i=0;i<n;i++)
#define repl(i,l,r) for(ll i=(l);i<(r);i++)
#define per(i,n) for(ll i=(n)-1;i>=0;i--)
#define perl(i,r,l) for(ll i=r-1;i>=l;i--)
#define fi first
#define se second
#define pb push_back
#define ins insert
#define pqueue(x) priority_queue<x,vector<x>,greater<x>>
#define all(x) (x).begin(),(x).end()
#define CST(x) cout<<fixed<<setprecision(x)
#define rev(x) reverse(x);
using ll=long long;
using vl=vector<ll>;
using vvl=vector<vector<ll>>;
using pl=pair<ll,ll>;
using vpl=vector<pl>;
using vvpl=vector<vpl>;
const ll MOD=1000000007;
const ll MOD9=998244353;
const int inf=2e9+1;
const ll INF=4e18;
const ll dy[8]={-1,0,1,0,1,1,-1,-1};
const ll dx[8]={0,-1,0,1,1,-1,1,-1};
template <typename T> inline bool chmax(T &a, T b) {
  return ((a < b) ? (a = b, true) : (false));
}
template <typename T> inline bool chmin(T &a, T b) {
  return ((a > b) ? (a = b, true) : (false));
}
int main(){
    ll n,p;cin >> n >> p;
    vl v(n);rep(i,n)cin >> v[i];
    vvl dp(n,vl(3,INF));//0なら<、1なら>,2なら_
    dp[0][1]=0;
    rep(i,n-1){
        chmin(dp[i+1][0],dp[i][0]+max(0LL,v[i]-v[i+1]));
        chmin(dp[i+1][0],dp[i][1]+max(0LL,v[i]-v[i+1])+p);
        chmin(dp[i+1][0],dp[i][2]+max(0LL,v[i]-v[i+1]));
        chmin(dp[i+1][1],dp[i][1]+max(0LL,v[i+1]-v[i]));
        chmin(dp[i+1][1],dp[i][0]+max(0LL,v[i+1]-v[i])+p);
        chmin(dp[i+1][1],dp[i][2]+max(0LL,v[i+1]-v[i]));
        chmin(dp[i+1][2],dp[i][0]+p);
        chmin(dp[i+1][2],dp[i][1]+p);
        chmin(dp[i+1][2],dp[i][2]+p);//ここはなくてもよさそう
    }
    cout << min({dp[n-1][0],dp[n-1][1],dp[n-1][2]}) << endl;
}