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//#pragma GCC optimize("Ofast", "unroll-loops")
//#pragma GCC target("sse", "sse2", "sse3", "ssse3", "sse4")

#include <bits/stdc++.h>

#define all(a) a.begin(),a.end()
#define len(a) (int)(a.size())
#define mp make_pair
#define pb push_back
#define fi first
#define se second

using namespace std;

typedef pair<int, int> pii;
typedef long long ll;
typedef long double ld;
template<class T>
using vec = vector<T>;

template<typename T>
bool umin(T &a, T b) {
    if (b < a) {
        a = b;
        return true;
    }
    return false;
}

template<typename T>
bool umax(T &a, T b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}

#ifdef KoRoVa
#define DEBUG for (bool _FLAG = true; _FLAG; _FLAG = false)
#define LOG(...) print(#__VA_ARGS__" ::", __VA_ARGS__) << endl

template<class ...Ts>
auto &print(Ts ...ts) { return ((cerr << ts << " "), ...); }

#else
#define DEBUG while (false)
#define LOG(...)
#endif

const int max_n = -1, inf = 1000111222;

void test_case() {
    ll n, k;
    cin>>n>>k;
    ll a[n];
    for(int i = 0; i < n; i++)
    {
        cin>>a[i];
    }
    ll ans = 0;
    bool ok = true;
    while(ok){
        ok = false;
        for(int i = 0; i < n - 1; i++)
        {
            if(a[i] + k < a[i + 1])
            {
                ans += a[i + 1] - k - a[i];
                a[i] = a[i + 1] - k;
                ok = true;
            }
            if(a[i + 1] + k < a[i])
            {
                ans += a[i] - k - a[i + 1];
                a[i + 1] = a[i] - k;
                ok = true;
            }
        }
    }
    cout<<ans<<'\n';
}

int main() {
//    freopen("input.txt", "r", stdin);
//    freopen("output.txt", "w", stdout);

    ios_base::sync_with_stdio(0);
    cin.tie(0);

    int t = 1;

    // cin >> t;

    while (t--) test_case();

    return 0;
}

/*
KoRoVa!
*/