#include <bits/stdc++.h>
//#define int LL
#define INF 2000000000
using namespace std;
typedef long long LL;

const int N = 5e3 + 10;

int a[N];
void solve()
{
    int n, d;
    cin >> n >> d;
    int val = INF;
    for (int i = 1; i <= n; i ++ ) {
        cin >> a[i];
        val = min(a[i], val);
    }

    int l = val, r = val + d;

    a[1] = min(r, a[1]);
    LL ans = 0;
    for (int i = 2; i <= n; i ++ ) {
        a[i] = min(r, a[i]);
        ans += abs(a[i] - a[i - 1]);
    }

    //for (int i = 1; i <= n; i ++ ) cout << a[i] << ' ';

    cout << ans;
}


signed main()
{
    int t = 1;
    while (t -- )
    {
        solve();
    }

    return 0;
}