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#include <iostream>
#include <vector>
#include <algorithm>

std::vector<int> v, max;

struct Greater {

	bool operator()(const int& a, const int& b) const {
		return v[a] > v[b];
	}

};

int main() {
	Greater greater;
	std::ios::sync_with_stdio(false);
	std::cin.tie();
	int n, k, x, old, w = 0;

	std::cin >> n >> k;
	
	for (int i = 0; i < n; i++) {
		std::cin >> x;
		v.push_back(x);
		max.push_back(i);
	}

	for (int i = 0; i < n - 1; i++) {
		std::sort(max.begin() + i, max.end(), greater);
		x = max[i];

		if (x != n - 1) {
			
			if (v[x] - v[x + 1] > k) {
				w += v[x] - v[x + 1] - k;
				v[x + 1] += v[x] - v[x + 1] - k;
			}

		}

		if (x != 0) {

			if (v[x] - v[x - 1] > k) {
				w += v[x] - v[x - 1] - k;
				v[x - 1] += v[x] - v[x - 1] - k;
			}

		}

	}

	std::cout << w;
	return 0;
}