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
#include <bits/stdc++.h>
using namespace std;
#define int long long
int32_t main() 
{
    cin.tie(0)->sync_with_stdio(0);
    int n;
    int k;
    cin >> n >> k;
    vector<int> a(n);
    for (int i = 0; i < n; i++) cin >> a[i];
    vector<int> h = a;
    for (int i = 1; i < n; i++) 
    {
        if (h[i] < h[i-1] - k) 
        {
            h[i] = h[i-1] - k;
        }
    }
    for (int i = n-2; i >= 0; i--) 
    {
        if (h[i] < h[i+1] - k) 
        {
            h[i] = h[i+1] - k;
        }
    }
    int res = 0;
    for (int i = 0; i < n; i++) 
    {
        res += (h[i] - a[i]);
    }
    cout << res;
    return 0;
}