#include <bits/stdc++.h>
#define ll long long
#define INF (1LL << 60)
#define MOD 1000000007
#define EPS 1e-10
#define rep(i,n) for(int i=0;i<(int)(n);++i)
#define rrep(i,n) for(int i=(int)(n)-1;i>=0;--i)
#define srep(i,s,t) for(int i=(int)(s);i<(int)(t);++i)
#define each(a,b) for(auto (a): (b))
#define all(v) (v).begin(),(v).end()
#define len(v) (int)(v).size()
#define zip(v) sort(all(v)),v.erase(unique(all(v)),v.end())
#define cmx(x,y) x=max(x,y)
#define cmn(x,y) x=min(x,y)
#define fi first
#define se second
#define pb push_back
#define show(x) cout<<#x<<" = "<<(x)<<endl
#define spair(p) cout<<#p<<": "<<p.fi<<" "<<p.se<<endl
#define svec(v) cout<<#v<<":";rep(kbrni,v.size())cout<<" "<<v[kbrni];cout<<endl
#define sset(s) cout<<#s<<":";each(kbrni,s)cout<<" "<<kbrni;cout<<endl
#define smap(m) cout<<#m<<":";each(kbrni,m)cout<<" {"<<kbrni.first<<":"<<kbrni.second<<"}";cout<<endl

using namespace std;

typedef pair<int,int> P;
typedef pair<ll,ll> pll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<ll> vl;
typedef vector<double> vd;
typedef vector<P> vp;
typedef vector<string> vs;

const int MAX_N = 200000;

ll dp1[MAX_N],dp2[MAX_N];

int main()
{
    int n;
    ll p;
    scanf("%d%lld",&n,&p);
    vl h(n);
    rep(i,n){
        scanf("%lld",&h[i]);
    }
    rep(i,n){
        dp1[i] = dp2[i] = INF;
    }
    dp1[0] = 0;
    rep(i,n-1){
        dp1[i+1] = min(min(dp1[i],dp2[i])+p,dp1[i]+max(h[i+1]-h[i],0LL));
        dp2[i+1] = min(min(dp1[i],dp2[i])+p,dp2[i]+max(h[i]-h[i+1],0LL));
    }
    cout << min(dp1[n-1],dp2[n-1]) << "\n";
    return 0;
}