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#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
typedef long long ll;
typedef long double ld;
#define pii pair<int,int>
#define vii vector<pair<int,int>>
#define vi vector<int>
#define pll pair<ll, ll>
#define all(x) (x).begin(),(x).end()
#define siz(x) (int)(x).size()
#define count_bits(x) __builtin_popcountll((x))
const ll M = 1e9+7;
const ll INF = 1e9;
//mt19937 mt;void random_start(){mt.seed(chrono::time_point_cast<chrono::milliseconds>(chrono::high_resolution_clock::now()).time_since_epoch().count());}
//ll los(ll a, ll b) {return a + (mt() % (b-a+1));}
typedef tree<int, null_type, less<int>, rb_tree_tag,tree_order_statistics_node_update> ordered_set;

const int MAXN = 1e3 + 5;
ll ans = 0;

ll A[MAXN];
ll isdone[MAXN];



int32_t main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    int n, k;
    cin >> n >> k;
    for(int i = 1; i <= n; ++i){
        cin >> A[i];
    }
    for(int i = 0; i < n; ++i){
        ll mxh = 0;
        ll ind = -1;
        for(int j = 1; j <= n; ++j){
            if(isdone[j]) continue;
            if(A[j] >= mxh){
                mxh = A[j];
                ind = j;
            }
        }
        for(auto u : {ind-1,ind+1}){
            if(u < 1 or u > n) continue;
            if(A[ind] - A[u] <= k) continue;
            ans += A[ind] - A[u] - k;
            A[u] = A[ind] - k;
        }
        isdone[ind] = 1;
    }
    cout << ans << "\n";

    return 0;
}