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#ifdef DEBUG
#define _GLIBCXX_DEBUG
#endif
//#pragma GCC optimize("O3")
#include<bits/stdc++.h>
using namespace std;

#ifdef DEBUG
#include "lib/debug.h"
#else
#define debug(...) 228
#endif


typedef long long ll;
typedef long double ld;

#define pb push_back
#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define F0R(i, a) FOR(i, 0, a)

vector<int> read_vec(int n) {
    vector<int> v(n);
    for (int& t : v) cin >> t;
    return v;
}

template<typename T>
inline void upd_max(T& a, T b) {
    if (a < b) {
        a = b;
    }
}

template<typename T>
inline void upd_min(T& a, T b) {
    if (a > b) {
        a = b;
    }
}

const int maxN = 1005;
int a[maxN];
int n, k;
int solve(int l, int r) {
    if (l >= r) return 0;
    int m = max_element(a + l, a + r + 1) - a;
    int d = 0;
    if (l < m && a[m - 1] + k < a[m]) {
        d += a[m] - a[m - 1] - k;
        a[m - 1] = a[m] - k;
    }
    if (m < r && a[m + 1] + k < a[m]) {
        d += a[m] - a[m + 1] - k;
        a[m + 1] = a[m] - k;
    }
    return d + solve(l, m - 1) + solve(m + 1, r);
}
int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
#ifdef DEBUG
    freopen("input.txt", "r", stdin);
#endif
    cin >> n >> k;
    FOR(i, 1, n + 1) cin >> a[i];
    ll ans = 0;
    cout << solve(1, n) << '\n';
    return 0;
}