1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
#include<bits/stdc++.h>
#define FOR(i,a,b) for(int i=a;i<b;++i)
#define FORD(i,a,b) for(int i=a;i>=b;--i)
#define PB push_back
#define EB emplace_back
#define FI first
#define SE second
#define umap unordered_map
#define uset unordered_set
#define vi vector<int>
#define vvi vector<vi>
#define vll vector<ll>
#define vvll vector<vll>
#define vpii vector<pii>
#define pii pair<int, int>
#define pll pair<ll, ll>
#define ALL(X) (X).begin(),(X).end()
#ifndef DEBUG
//#define endl (char)10
#endif
using namespace std;
using ll = long long;
using ld = long double;

template <class T>
ostream& operator<< (ostream& os, const vector<T>& vec){
    for(auto& t : vec) os << t << " ";
    return os;
}
template<class T, class U>
ostream& operator<< (ostream& os, const pair<T, U>& p){
    os << p.FI << " " << p.SE;
    return os;
}
template<class T, class U>
istream& operator>> (istream& is, pair<T, U>& p){
    is >> p.FI >> p.SE;
    return is;
}
template <class T>
istream& operator>> (istream& is, vector<T>& vec){
    for(auto& p : vec) is >> p;
    return is;
}

int solve(vi& V, int k, int b, int e) {
	//cout << b << " " << e << ": " << V << endl;
	if (e <= b + 1) return 0;
	int i = max_element(V.begin() + b, V.begin() + e) - V.begin();
	int ans = 0;
	if (i > b) {
		int miniv = max(V[i - 1], V[i] - k);
		ans += miniv - V[i - 1];
		V[i - 1] = miniv;
		ans += solve(V, k, b, i);
	}
	if (i < e - 1) {
		int miniv = max(V[i + 1], V[i] - k);
		ans += miniv - V[i + 1];
		V[i + 1] = miniv;
		ans += solve(V, k, i + 1, e);
	}
	return ans;
}

int main () {
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    int n, k;
    cin >> n >> k;
    
    vi V(n);
    cin >> V;
    cout << solve(V, k, 0, n) << endl;
    
    
}