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 rep(a, b) for (int a = 0; a < (b); a++)
#define rep1(a, b) for (int a = 1; a <= (b); a++)
#define all(x) (x).begin(), (x).end()
using ll = long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
const int MOD = 1e9 + 7;

const int LIM = 1007;
int n, k;

int nums[LIM];

int main() {
    ios_base::sync_with_stdio(0); cin.tie(0);
    
    cin >> n >> k;
    rep(i, n) cin >> nums[i];

    ll cnt = 0;
    rep1(i, n-1) if (nums[i] < nums[i-1]-k) {
        cnt += nums[i-1]-k-nums[i];
        nums[i] = nums[i-1]-k;
    }
    for (int i = n-2; i >= 0; i--) if (nums[i] < nums[i+1]-k) {
        cnt += nums[i+1]-k-nums[i];
        nums[i] = nums[i+1]-k;
    }
    cout << cnt << "\n";

    return 0;
}