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#include <iostream>
#include <vector>

typedef std::vector<int32_t> vect;
void print(vect &v) {
	for (int32_t i = 0; i < v.size(); ++i) {
		std::cerr << v[i] << " ";
	}
	std::cerr << "\n";
}

int32_t alignRight(int32_t idx, int32_t k, vect &v);

int32_t alignLeft(int32_t idx, int32_t k, vect &v) {
	int32_t result = 0;
	for (int32_t i = idx; i >= 0; --i) {
		if (i > 0) {
			int32_t numCont = 0;
			int32_t diff = v[i] - v[i - 1];
			if (diff > k) {
				numCont = diff - k;
				v[i - 1] += numCont;
			} else if (diff < (-k)) {
				numCont = ((-1) * diff) - k;
				v[i] += numCont;
				numCont += alignRight(i, k, v);
			}
			result += numCont;
//			print(v);
		}
	}
	return result;
}


int32_t alignRight(int32_t idx, int32_t k, vect &v) {
	int32_t result = 0;
	for (int32_t i = idx; i < v.size(); ++i) {
		if (i < v.size() - 1) {
			int32_t numCont = 0;
			int32_t diff = v[i] - v[i + 1];
			if (diff > k) {
				numCont = diff - k;
				v[i +1] += numCont;
			} else if (diff < (-k)) {
				numCont = ((-1) * diff) - k;
				v[i] += numCont;
				numCont += alignLeft(i, k, v);
			}
			result += numCont;
//			print(v);
		}
	}
	return result;
}


void prog_main(std::istream& in, std::ostream& out)
{
	int32_t n = 0;
	int32_t k = 0;
	in >> n;
	in >> k;
	vect v(n, 0);
	int32_t maxId = 0;

	for (int32_t i = 0; i < v.size(); ++i) {
		in >> v[i];
		if (v[maxId] < v[i]) {
			maxId = i;
		}
	}
//	print(v);
	int32_t result = alignLeft(maxId, k, v);
	result += alignRight(maxId, k, v);
	out << result;
}

#ifndef TEST
int main(int argc, char* argv[])
{
	prog_main(std::cin, std::cout);
	return 0;
}
#endif