#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, c, min = 101, p = 0;
  cin >> n >> c;
  int a[n];
  for (int i = 0; i < n; ++i) {
    cin >> a[i];
  }
  for (int i = 0; i < n - 1; i++) {
    p = max(p, a[i] - a[i + 1] - c);
  }
  cout << p;
}
