#include <algorithm>
#include <cassert>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <iostream>
#include <numeric>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <functional>
#include <iomanip>
using namespace std;
using ll = long long;

class range {private: struct I{int x;int operator*(){return x;}bool operator!=(I& lhs){return x<lhs.x;}void operator++(){++x;}};I i,n;
public:range(int n_):i({0}),n({n_}){}range(int i_,int n_):i({i_}),n({n_}){}I& begin(){return i;}I& end(){return n;}};


template<class T, class U> ostream& operator<<(ostream& os, const pair<T, U>& p){ return os << "{" << p.first << ", " << p.second << "}"; }
template<typename T> ostream& operator<<(ostream& os, const vector<T>& obj) { os << "{"; for (const auto& e : obj) os << e << ", "; return os << "}"; }
template<typename T> ostream& operator<<(ostream& os, const set<T>& obj) { os << "set{"; for (const auto& e : obj) os << e << ", "; return os << "}"; }
template<typename T, typename U> ostream& operator<<(ostream& os, const map<T, U>& obj) { os << "map{"; for (const auto& e : obj) os << e << ", "; return os << "}"; }

#ifdef ONLINE_JUDGE
#define dump(expr) ;
#else
#define dump(expr) { cerr << "\033[33m#L" << __LINE__ << ": " << expr << "\033[39m" << endl; }
#endif

ll solve() {
  ll n, p; cin >> n >> p;
  vector<ll> vh(n);
  for (int i : range(n)) cin >> vh[i];

  vector<vector<ll>> dp(n + 1, vector<ll>(2));
  for (int i = n - 1; i >= 0; --i) {
    for (int dir : range(2)) {
      // dir = 0  =>  go right
      // dir = 1  =>  go left
      dp[i][dir] = p + min(dp[i + 1][0], dp[i + 1][1]);
      if (i < n - 1) {
        ll climb = max(vh[i + 1] - vh[i], 0LL);
        if (dir) climb = max(vh[i] - vh[i + 1], 0LL);
        dp[i][dir] = min(dp[i][dir], climb + dp[i + 1][dir]);
      }
    }
  }

  ll res = 1LL << 60;
  ll curr = 0;
  for (int i : range(n)) {
    res = min(res, curr + min(dp[i + 1][0], dp[i + 1][1]));

    if (i < n - 1) curr += max(vh[i + 1] - vh[i], 0LL);
  }

  return res;
}

int main() {
  cout << fixed << setprecision(12);
  cout << solve() << endl;
}