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#include <iostream>
#include <vector>
#include <set>
#include <map>
#include <algorithm>
#include <unordered_map>
#include <unordered_set>
#include <queue>
#include <deque>
#include <tuple>
#include <bitset>

using namespace std;

#define pb push_back
#define mp make_pair
#define st first
#define nd second
#define x first
#define y second

typedef long long ll;
typedef pair<ll, ll> pii;
typedef pair<ll, ll> pll;
typedef vector<ll> vi;
typedef vector<ll> vll;

vll A;
ll n;


int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    
    int n, k;
    cin >> n >> k;
    
    vll A(n);
    
    for(auto &a: A){
        cin >> a;
    }
    
    ll ans = 0;
    
    for(int i=0; i<n; i++){
        for(int j=0; j<n; j++){
            ll l = j==0 ? A[j] : A[j-1];
            ll r = j==n-1 ? A[j] : A[j+1];
            ll m = max(l, r);
            ll d = m-(A[j]+k);
            if(d>0){
                A[j] += d;
                ans += d;
                
            }
        }
    }
    
    cout << ans << "\n";


    return 0;
}