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#include <bits/stdc++.h>
#define FOR(i, a, b) for(int i = (int)a; i <= (int)b; ++i)
#define RFOR(i, a, b) for(int i = (int)a; i >= (int)b; --i)
#define in insert
#define pb push_back
#define fi first
#define se second
#define ll long long
#define ull unsigned long long
using namespace std;

const int MAX = 1005;
ll tab[MAX];

void solve() {
    ll n, k; cin >> n >> k;
    FOR(i, 1, n) cin >> tab[i];
    ll res = 0;
    while(true) {
        bool tf = true;
        FOR(i, 1, n - 1) {
            if(abs(tab[i] - tab[i + 1]) > k) tf = false;
        }
        if(tf) break;
        FOR(i, 1, n) {
            if(tab[i + 1] - tab[i] > k) {
                ll roz = tab[i + 1] - tab[i];
                roz = roz - k;
                res += roz;
                tab[i] += roz;
            }
        }
        RFOR(i, n, 1) {
            if(tab[i - 1] - tab[i] > k) {
                ll roz = tab[i - 1] - tab[i];
                roz = roz - k;
                res += roz;
                tab[i] += roz;
            }
        }
    }
    cout << res;
}

int main() {
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    solve();
    return 0;
}