#include<bits/stdc++.h>

using namespace std;

using int64 = long long;
const int mod = 1e9 + 7;

const int64 infll = (1LL << 62) - 1;
const int inf = (1 << 30) - 1;

struct IoSetup {
  IoSetup() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(10);
    cerr << fixed << setprecision(10);
  }
} iosetup;


template< typename T1, typename T2 >
ostream &operator<<(ostream &os, const pair< T1, T2 > &p) {
  os << p.first << " " << p.second;
  return os;
}

template< typename T1, typename T2 >
istream &operator>>(istream &is, pair< T1, T2 > &p) {
  is >> p.first >> p.second;
  return is;
}

template< typename T >
ostream &operator<<(ostream &os, const vector< T > &v) {
  for(int i = 0; i < (int) v.size(); i++) {
    os << v[i] << (i + 1 != v.size() ? " " : "");
  }
  return os;
}

template< typename T >
istream &operator>>(istream &is, vector< T > &v) {
  for(T &in : v) is >> in;
  return is;
}

template< typename T1, typename T2 >
inline bool chmax(T1 &a, T2 b) { return a < b && (a = b, true); }

template< typename T1, typename T2 >
inline bool chmin(T1 &a, T2 b) { return a > b && (a = b, true); }

template< typename T = int64 >
vector< T > make_v(size_t a) {
  return vector< T >(a);
}

template< typename T, typename... Ts >
auto make_v(size_t a, Ts... ts) {
  return vector< decltype(make_v< T >(ts...)) >(a, make_v< T >(ts...));
}

template< typename T, typename V >
typename enable_if< is_class< T >::value == 0 >::type fill_v(T &t, const V &v) {
  t = v;
}

template< typename T, typename V >
typename enable_if< is_class< T >::value != 0 >::type fill_v(T &t, const V &v) {
  for(auto &e : t) fill_v(e, v);
}

template< typename F >
struct FixPoint : F {
  FixPoint(F &&f) : F(forward< F >(f)) {}

  template< typename... Args >
  decltype(auto) operator()(Args &&... args) const {
    return F::operator()(*this, forward< Args >(args)...);
  }
};

template< typename F >
inline decltype(auto) MFP(F &&f) {
  return FixPoint< F >{forward< F >(f)};
}

template< typename T = int >
struct Edge {
  int from, to;
  T cost;
  int idx;

  Edge() = default;

  Edge(int from, int to, T cost = 1, int idx = -1) : from(from), to(to), cost(cost), idx(idx) {}

  operator int() const { return to; }
};

template< typename T = int >
struct Graph {
  vector< vector< Edge< T > > > g;
  int es;

  Graph() = default;

  explicit Graph(int n) : g(n), es(0) {}

  size_t size() const {
    return g.size();
  }

  void add_directed_edge(int from, int to, T cost = 1) {
    g[from].emplace_back(from, to, cost, es++);
  }

  void add_edge(int from, int to, T cost = 1) {
    g[from].emplace_back(from, to, cost, es);
    g[to].emplace_back(to, from, cost, es++);
  }

  void read(int M, int padding = -1, bool weighted = false, bool directed = false) {
    for(int i = 0; i < M; i++) {
      int a, b;
      cin >> a >> b;
      a += padding;
      b += padding;
      T c = T(1);
      if(weighted) cin >> c;
      if(directed) add_directed_edge(a, b, c);
      else add_edge(a, b, c);
    }
  }
};

template< typename T = int >
using Edges = vector< Edge< T > >;


/**
 * @brief Skew-Heap
 */
template< typename T, bool isMin = true >
struct SkewHeap {
  struct Node {
    T key, lazy;
    Node *l, *r;
    int idx;

    explicit Node(const T &key, int idx) : key(key), idx(idx), lazy(0), l(nullptr), r(nullptr) {}
  };

  SkewHeap() = default;

  Node *alloc(const T &key, int idx = -1) {
    return new Node(key, idx);
  }

  Node *propagate(Node *t) {
    if(t && t->lazy != 0) {
      if(t->l) t->l->lazy += t->lazy;
      if(t->r) t->r->lazy += t->lazy;
      t->key += t->lazy;
      t->lazy = 0;
    }
    return t;
  }

  Node *meld(Node *x, Node *y) {
    propagate(x), propagate(y);
    if(!x || !y) return x ? x : y;
    if((x->key < y->key) ^ isMin) swap(x, y);
    x->r = meld(y, x->r);
    swap(x->l, x->r);
    return x;
  }

  Node *push(Node *t, const T &key, int idx = -1) {
    return meld(t, alloc(key, idx));
  }

  Node *pop(Node *t) {
    assert(t != nullptr);
    return meld(t->l, t->r);
  }

  Node *add(Node *t, const T &lazy) {
    if(t) {
      t->lazy += lazy;
      propagate(t);
    }
    return t;
  }

  Node *make_root() {
    return nullptr;
  }
};


/**
 * @brief Directed-Minimum-Spanning-Tree(最小有向全域木)
 */
template< typename T >
struct MinimumSpanningTree {
  T cost;
  Edges< T > edges;
};

template< typename T >
MinimumSpanningTree< T > directed_minimum_spanning_tree(long long V, long long root, Edges< T > edges) {
  for(int i = 0; i < V; ++i) {
    if(i != root) edges.emplace_back(i, root, 0);
  }

  int x = 0;
  vector< int > par(2 * V, -1), vis(par), link(par);

  using Heap = SkewHeap< T, true >;
  using Node = typename Heap::Node;

  Heap heap;
  vector< Node * > ins(2 * V, heap.make_root());

  for(int i = 0; i < (int) edges.size(); i++) {
    auto &e = edges[i];
    ins[e.to] = heap.push(ins[e.to], e.cost, i);
  }
  vector< int > st;
  auto go = [&](int x) {
    x = edges[ins[x]->idx].from;
    while(link[x] != -1) {
      st.emplace_back(x);
      x = link[x];
    }
    for(auto &p : st) {
      link[p] = x;
    }
    st.clear();
    return x;
  };
  for(int i = V; ins[x]; i++) {
    for(; vis[x] == -1; x = go(x)) vis[x] = 0;
    for(; x != i; x = go(x)) {
      auto w = ins[x]->key;
      auto v = heap.pop(ins[x]);
      v = heap.add(v, -w);
      ins[i] = heap.meld(ins[i], v);
      par[x] = i;
      link[x] = i;
    }
    for(; ins[x] && go(x) == x; ins[x] = heap.pop(ins[x]));
  }
  T cost = 0;
  Edges< T > ans;
  for(int i = root; i != -1; i = par[i]) {
    vis[i] = 1;
  }
  for(int i = x; i >= 0; i--) {
    if(vis[i] == 1) continue;
    cost += edges[ins[i]->idx].cost;
    ans.emplace_back(edges[ins[i]->idx]);
    for(int j = edges[ins[i]->idx].to; j != -1 && vis[j] == 0; j = par[j]) {
      vis[j] = 1;
    }
  }
  return {cost, ans};
}
using ll=long long;
using vl=vector<ll>;
#define rep(i,n) for(ll i=0;i<n;i++)
int main() {
    ll n,p;cin >> n >>p;
    vl v(n);rep(i,n)cin >> v[i];
    Edges<ll> eds;
    rep(i,n-1){
        eds.emplace_back(i,i+1,max(0LL,v[i+1]-v[i]));
        eds.emplace_back(i+1,i,max(0LL,v[i]-v[i+1]));
    }
    rep(i,n){
        if(!i)eds.emplace_back(n,i,0);
        else eds.emplace_back(n,i,p);
    }
    ll ans=directed_minimum_spanning_tree(n+1,n,eds).cost;
    cout << ans << endl;
}