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#include <vector>
#include <cstdio>
#include <stack>
#include <algorithm>
#include <queue>
#include <map>
#include <cmath>
#include <unordered_set>
#include <unordered_map>
#include <set>
#include <cstring>
#include <bitset>
#include <iostream>
#include <queue>
#include <iomanip>
#include <complex>

using namespace std;

#define ALL(x) x.begin(), x.end()
#define UNIQUE(c) (c).resize(unique(ALL(c)) - (c).begin())
#define FOR(i, a, b) for(int i =(a); i <=(b); ++i)
#define RE(i, n) FOR(i, 1, n)
#define RED(i, n) FORD(i, n, 1)
#define FORD(i, a, b) for(int i = (a); i >= (b); --i)
#define REP(i, n) for(int i = 0;i <(n); ++i)
#define REPD(i, n) FORD(i, n-1,0)

#define printA(a, L, R) FOR(i,L,R) cout << a[i] << (i==R?'\n':' ')
#define printV(a) printA(a,0,a.size()-1)
#define PRESENT(c, x) ((c).find(x) != (c).end())
#define CPRESENT(c, x) (find(ALL(c),x) != (c).end())
#define bit(x, i) (x&(1<<i))
#define lowbit(x) ((x)&((x)^((x)-1)))

const int fx[4][2] = {
    {0, 1},
    {1, 0},
    {0, -1},
    {-1, 0}
};
const int fxx[8][2] = {
    {0, 1},
    {0, -1},
    {1, 0},
    {-1, 0},
    {1, 1},
    {1, -1},
    {-1, 1},
    {-1, -1}
};
const int sk[8][2] = {
    {2, 1},
    {2, -1},
    {-2, -1},
    {-2, 1},
    {1, 2},
    {-1, 2},
    {1, -2},
    {-1, -2}
};

const int maxa = 202112, maxn = 500024, maxp = 60;
const long long maxc = 40002, maxc2 = 25002, inf = 4000000000000000001ll;
const long long mod = 1000000007ll;
long long pot(long long a, long long b) {
    if (b == 0) return 1;
    if (b&1) return (pot(a, b - 1) * a) % mod;
    long long c = pot(a, b / 2);
    return (c * c) % mod;
}
long long ans, n, k, a[1002];
void solve() {
    cin>>n>>k;
    REP(i, n)cin>>a[i];
    REP(i, n) {
        REP(j, n) {
            if (j > 0 && a[j - 1] - k > a[j]) {
                ans += a[j - 1] - k - a[j];
                a[j] = a[j - 1] - k;
            }
            if (j < n - 1 && a[j + 1] - k > a[j]) {
                ans += a[j + 1] - k - a[j];
                a[j] = a[j + 1] - k;
            }
        }
    }
    cout << ans << endl;
}

int main() {
    ios_base::sync_with_stdio(false), cin.tie(nullptr);
    int tt = 1;
    // cin >> tt;
    while (tt--) {
        solve();
    }
    return 0;
}