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#include <bits/stdc++.h>
#define rep(i, p, k) for (int i = (p); i < (k); ++i)
#define all(v) (v).begin(), (v).end()
#define ll long long
#define fi first
#define sc second
#ifndef DEBUG
#define debug(...)
#else
#include "debug.h"
#endif
using namespace std;

int main() {
  cin.tie(0)->sync_with_stdio(0);
  int n, k;
  cin >> n >> k;
  int r = 0;
  vector<int> h(n);
  for (auto &v : h)
    cin >> v;
  for (int i = 0; i < n; i++) {
    for (int j = 0; j < n; j++) {
      int m = 0;
      if (j)
        m = max(m, h[j - 1]);
      if (j != n - 1)
        m = max(m, h[j + 1]);
      if (h[j] + k < m) {
        r += m - h[j] - k;
        h[j] = m - k;
      }
    }
  }
  cout << r << '\n';
}