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// Karol Kosinski 2026
#include <bits/stdc++.h>
#define FOR(i,a,b) for(int i=(a),_b=(b);i<_b;++i)
#define FR_(i,a,b) for(int i=(a),_b=(b);i<=_b;++i)
#define FD_(i,b,a) for(int i=(b),_a=(a);i>=_a;--i)
#define ALL(c) (c).begin(),(c).end()
#define SIZE(c) int((c).size())
#define X first
#define Y second
#define endl '\n'
#define NAM(x) #x,'=',x
using namespace std;
using LL = long long;
using ULL = unsigned long long;
using PII = pair<int, int>;
using TIII = tuple<int, int, int>;
template<class...T> void _cout(T...a){(cout<<...<<a);}

#ifndef ENABLE_DEBUG
#define DEB(k,p,f,x...)
#else
#define DEB(k,p,f,x...) {if(k)_cout("------",setw(4),__LINE__," : ",__FUNCTION__,endl);if(p)f(x);}
#endif
#define DEBF(f,x...)    DEB(1,1,f,x)
#define DEBL            DEBF(void,0)
#define DEBC(p,x...)    DEB(0,p,_cout,x)
#define DEBUG(x...)     DEBC(1,x)

constexpr int NX = 1'005;

LL A[NX];
priority_queue<pair<LL, LL>> Q;

LL solve()
{
    LL n, k, res = 0;
    cin >> n >> k;
    FOR(i,0,n)
    {
        cin >> A[i];
        Q.emplace( A[i], i );
    }
    while ( not Q.empty() )
    {
        auto [w, ind] = Q.top(); Q.pop();
        if ( A[ind] != w ) continue;
        if ( 0 < ind )
        {
            LL &aa = A[ ind-1 ];
            LL rd = abs(w - aa) - k;
            if ( rd > 0 )
            {
                res += rd;
                aa += rd;
                Q.emplace( aa, ind-1 );
            }
        }
        if ( ind < n-1 )
        {
            LL &aa = A[ ind+1 ];
            LL rd = abs(w - aa) - k;
            if ( rd > 0 )
            {
                res += rd;
                aa += rd;
                Q.emplace( aa, ind+1 );
            }
        }
    }
    return res;
}

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    cout << solve() << endl;
    return 0;
}