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


int main() {
	ios_base::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	LL n, k;
	cin>>n>>k;
	vector<LL> v(n);
	vector<bool> done(n);
	for(auto &x : v)cin>>x;
	LL res = 0;
	for(int i=0; i<n; i++){
		pair<LL, int> maxi = {0, -1};
		for(int j=0; j<n; j++){
			if(done[j])continue;
			if(maxi.first < v[j]){
				maxi = {v[j], j};
			}
		}
		int id = maxi.second;
		if(id>0 && v[id-1] + k < v[id]){
			LL diff = v[id] - (v[id-1] + k);
			res += diff;
			v[id-1] += diff;
		}
		if(id<n-1 && v[id+1] + k < v[id]){
			LL diff = v[id] - (v[id+1] + k);
			res += diff;
			v[id+1] += diff; 
		}
		done[id]=true;
	}
	
	cout<<res<<"\n";
	return 0;
}