#include <bits/stdc++.h>
#define N 1001
#define INF 1000000000

using namespace std;

int n, k;
int a[N];
int ma, mi;
int w;
int d;

int main() {

    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);

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

    w = 0;
    for (int j = 0; j < n; j++) {
        ma = 0;
        mi = 0;

        for (int i = 0; i < n; i++) {
            if (a[i] > ma && a[i] != INF) {
                ma = a[i];
                mi = i;
            }
        }
        if (mi > 0) {
            d = a[mi] - a[mi - 1];
            w += max(d - k, 0);
            a[mi - 1] += max(d - k, 0);
        }
        if (mi < n - 1) {
            d = a[mi] - a[mi + 1];
            w += max(d - k, 0);
            a[mi + 1] += max(d - k, 0);
        }
        a[mi] = INF;
    }
    cout << w <<"\n";
    return 0;
}