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#include <bits/stdc++.h>

using namespace std;

int dp[1010];

int adjust(const int a, const int b, const int k) {
    const int diff = a - b;
    if (diff <= k) return 0;
    return diff - k;
}

int main() {
    ios::sync_with_stdio(false); cin.tie(nullptr);

    int n, k; cin >> n >> k;

    for (int i = 1; i <= n; i++) cin >> dp[i];

    int ans = 0;

    for (int i = 1; i < n; i++) {
        const int adj = adjust(dp[i], dp[i+1], k);
        dp[i+1] += adj;
        ans += adj;
    }
    for (int i = n-1; i >= 1; i--) {
        const int adj = adjust(dp[i+1], dp[i], k);
        dp[i] += adj;
        ans += adj;
    }
    cout << ans << "\n";
}