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#include<bits/stdc++.h>
using namespace std;

#define rep(i, a, b) for (int i = (a); i < (b); i++)
#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()
#define ST first
#define ND second
#define PB push_back
using ll = long long;
using ld = long double;
using pi = pair<int,int>;
using vi = vector<int>;
using vvi = vector<vi>;
using vll = vector<ll>;


#ifdef LOCAL
#define DTP(x, y)                                    \
    auto operator<<(auto &o, auto a)->decltype(y, o) \
    {                                                \
        o << "(";                                    \
        x;                                           \
        return o << ")";                             \
    }
DTP(o << a.first << ", " << a.second, a.second);
DTP(for (auto i : a) o << i << ", ", all(a));
void dump(auto... x) { ((cerr << x << ", "), ...) << '\n'; }
#define debug(x...) cerr << setw(4) << __LINE__ << ":[" #x "]: ", dump(x)
#else
#define debug(...) 0
#endif



void Solve()
{
    int n, k;
    cin >> n >> k;
    vll A(n);
    ll res=0;
    vi Used(n);
    for(auto &a: A)
        cin >> a;
    int cnt=n;
    while(cnt--){
        ll m0=0;
        ll m1=0;
        rep(i, 0, n){
            if(A[i]>=m0 && !Used[i]){
                m0=A[i];
                m1=i;
            }
        }
        Used[m1]=1;
        if(m1>0){
            if(A[m1]-k>A[m1-1]){
                res+=(A[m1]-k-A[m1-1]);
                A[m1-1]=A[m1]-k;
            }
        }if(m1<n-1){
            if(A[m1]-k>A[m1+1]){
                res+=A[m1]-k-A[m1+1];
                A[m1+1]=A[m1]-k;
            }
        }
    }
    cout << res << "\n";
    return;
}

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    int t=1;
    // cin >> t;
    while(t--)
    {
        Solve();
    }
    return 0;
}