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

int main() {
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);

	int n, k;
	cin >> n >> k;
	vector <int> v(n);
	for (int i = 0; i < n; i++) {
		cin >> v[i];
	}
	int res = 0;
	for (int i = 1; i < n; i++) {
		if (v[i] < v[i-1] - k) {
			res += (v[i-1] - k - v[i]);
			v[i] += (v[i-1] - k - v[i]);
		}
		for (int j = i-1; j >= 0; j--) {
			if (v[j+1] > v[j] + k) {
				res += (v[j+1] - k - v[j]);
				v[j] += (v[j+1] - k - v[j]);
			}
		}
	}
	cout << res;
}