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#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define FOR(i,a,b) for (__typeof(b) i = a; i < b; ++i)
#define FORev(i,a,b) for(__typeof(a) i = a; i >= b; --i)
#define c(x) cin >> x;
#define elif else if

signed main(){
    ios::sync_with_stdio(0);
    cin.tie(0);
    ll n,k; c(n); c(k);
    vector<ll> tab(n);
    for (auto& x : tab) c(x);
    ll res = 0;
    FOR(i,0,n-1){
        ll tmp = abs(tab[i]-tab[i+1]);
        if (tmp <= k)
            continue;
        elif (tab[i] > tab[i+1])
            tab[i+1] += (tmp-k);
        else 
            tab[i] += (tmp-k);
        res += tmp-k;
    }
    FORev(i,n-1,1){
        ll tmp = abs(tab[i]-tab[i-1]);
        if (tmp <= k)
            continue;
        elif (tab[i] > tab[i-1])
            tab[i-1] += (tmp-k);
        else 
            tab[i] += (tmp-k);
        res += tmp-k;
    }
    cout << res << "\n";
}