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#include <bits/stdc++.h>

using namespace std;

#define SCALAR(x) \
int x; \
cin >> x;

#define SCALAR_LONG(x) \
long long x; \
cin >> x;

#define VECTOR(v, n) \
vector<int> v(n); \
for (int i = 0; i < n; ++i) \
cin >> v[i];

#define PAIR_VECTOR(v, pair_class, n) \
vector<pair_class> v; \
for (int _ = 0; _ < n; ++_) { \
SCALAR(first);  \
SCALAR(second); \
v.push_back({first, second}); \
}

#define PRINT(expr) \
cout << expr << '\n';

#define PRINT_IF(condition) \
auto message = condition ? "Yes" : "No"; \
PRINT(message)

#define BOOST_IO() \
ios::sync_with_stdio(false); \
cin.tie(nullptr);

void solve();

int main()
{
    BOOST_IO()
    solve();
}

void solve() {
    SCALAR(n)
    SCALAR(k)

    VECTOR(as, n)

    auto total_truck_count = 0;

    bool truck_was_used;

    do {
        truck_was_used = false;
        for (int i = 0; i < n - 1; ++i) {
            auto growth = as[i + 1] - as[i];

            if (growth > k) {
                auto truck_count = growth - k;

                as[i] += truck_count;
                total_truck_count += truck_count;

                truck_was_used = true;
            }
            else if (growth < -k) {
                auto truck_count = -k - growth;

                as[i + 1] += truck_count;
                total_truck_count += truck_count;

                truck_was_used = true;
            }
        }
    } while (not truck_was_used);

    PRINT(total_truck_count)
}