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
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
#include <bits/stdc++.h>

using namespace std;

int n, k;
int *a;

int L, R;

int gravel = 0;

int diff(int a, int b)
{
    return abs(a - b);
}

void drop_gravel(int center)
{
    int lp = center - 1;
    int rp = center + 1;

    while (lp >= L || rp <= R)
    {
        if (lp >= L)
        {
            if (diff(a[lp], a[lp + 1]) > k)
            {
                if (a[lp] > a[lp + 1])
                {
                    drop_gravel(lp);
                    lp = L - 1;
                }
                else
                {
                    gravel += a[lp + 1] - a[lp] - k;
                    a[lp] = a[lp + 1] - k;
                }
            }

            lp--;
        }

        if (rp <= R)
        {
            if (diff(a[rp], a[rp - 1]) > k)
            {
                if (a[rp] > a[rp - 1])
                {
                    drop_gravel(rp);
                    rp = R + 1;
                }
                else
                {
                    gravel += a[rp - 1] - a[rp] - k;
                    a[rp] = a[rp - 1] - k;
                }
            }

            rp++;
        }
    }
}

int main()
{
    std::ios_base::sync_with_stdio(false);
    std::cin.tie(NULL);

    cin >> n >> k;
    L = 0;
    R = n - 1;

    a = new int[n];

    int max_index = 0;

    for (int i = 0; i < n; i++)
    {
        cin >> a[i];

        if (a[i] > a[max_index])
        {
            max_index = i;
        }
    }

    drop_gravel(max_index);

    cout << gravel << endl;

    delete[] a;
    return 0;
}