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#include <vector>
#include <iostream>

using namespace std;

typedef long long int ll;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int n, k;

    cin >> n >> k;

    vector<int> numbers;
    vector<bool> checked(n, false);

    for(int i = 0; i < n; i++){
        int number;
        cin >> number;
        numbers.push_back(number);
    }


    int ans = 0;

    for(int i = 0; i < n; i++){
        int max_ind = -1;
        for(int j = 0; j < n; j++){
            if(!checked[j] && (max_ind == -1 || numbers[max_ind] < numbers[j])){
                max_ind = j;
            }
        }

        int left = max(0, max_ind - 1);
        int right = min(n - 1, max_ind + 1);

        for (int neighbor: {left, right}){
            if(numbers[max_ind] > numbers[neighbor] + k){
                int diff = numbers[max_ind] - numbers[neighbor] - k;
                numbers[neighbor] += diff;
                ans += diff;
            }
        }


        checked[max_ind] = true;
    }
        
    cout << ans << endl;
    return 0;
}