/* -*- coding: utf-8 -*-
 *
 * 595.cc: No.595 登山 - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

const int MAX_N = 200000;

/* typedef */

typedef long long ll;

/* global variables */

int hs[MAX_N];
ll dpr[MAX_N], dpl[MAX_N];

/* subroutines */

inline ll minll(ll a, ll b) { return (a < b) ? a : b; }
inline ll maxll(ll a, ll b) { return (a > b) ? a : b; }
inline void setmin(ll &a, ll b) { if (a > b) a = b; }

/* main */

int main() {
  int n, p;
  scanf("%d%d", &n, &p);

  for (int i = 0; i < n; i++) scanf("%d", &hs[i]);

  dpr[0] = 0;
  dpl[0] = p;
  for (int i = 1; i < n; i++) {
    ll dp0 = min(dpr[i - 1], dpl[i - 1]) + p;
    dpr[i] = min(dp0, dpr[i - 1] + max(0, hs[i] - hs[i - 1]));
    dpl[i] = min(dp0, dpl[i - 1] + max(0, hs[i - 1] - hs[i]));
    //printf("%d: dpr=%lld, dpl=%lld\n", i, dpr[i], dpl[i]);
  }

  printf("%lld\n", min(dpr[n - 1], dpl[n - 1]));
  return 0;
}