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#include <bits/stdc++.h>
using namespace std;

int main() {
  int n, k;
  cin >> n >> k;
  vector<int> arr(n);
  for (int& v : arr) {
    cin >> v;
  }
  long long res = 0;
  for (int i = 0; i < n; i++) {
    for (int j = 0; j < n-1; j++) {
      int add = max(0, arr[j+1] - arr[j] - k);
      res += add;
      arr[j] += add;
      add = max(0, arr[j] - arr[j+1] - k);
      arr[j+1] += add;
      res += add;
    }
  }
  cout << res << endl;
}