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

ll n, k;
ll tab[1007];

ll out=0;

int main() {
    ios_base::sync_with_stdio(0); cin.tie(0);
    
    cin >> n >> k;
    for (ll i=0; i<n; i++) cin >> tab[i];
    
    for (ll _=0; _<n; _++) {
        for (ll i=0; i<n-1; i++) {
        
            if (tab[i] < tab[i+1]) {
                
                if (tab[i+1]-k <= tab[i]) continue;
                
                out += tab[i+1]-k - tab[i];
                tab[i] = tab[i+1]-k;
                
            } else {
                
                if (tab[i]-k <= tab[i+1]) continue;
                
                out += tab[i]-k - tab[i+1];
                tab[i+1] = tab[i]-k;
                
            }
        }
    }
    
    // for (int i=0; i<n; i++) cout << tab[i] << ' ';
    // cout << endl;
    cout << out << "\n";
    
    return 0;
}