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

int main() {
	cin.tie(0); ios_base::sync_with_stdio(0);
	int n, k;
	cin >> n >> k;
	vector<int> a(n), b(n);
	for (int i = 0; i < n; i++) {
		cin >> a[i];
	}
	b[0] = max(b[0], a[0]);
	for (int i = 1; i < n; i++) {
		b[i] = max(a[i], b[i - 1] - k);
	}
	b[n - 1] = max(b[n - 1], a[n - 1]);
	for (int i = n - 1; i >= 0; i--) {
		b[i] = max(b[i], max(a[i], b[i + 1] - k));
	}
	int ans = 0;
	for (int i = 0; i < n; i++) {
		ans += b[i] - a[i];
	}
	cout << ans << '\n';
}