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#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define imie(x...) cerr << "[" #x "]: ", [](auto... $) {((cerr << $ << "; "), ...); }(x), cerr << '\n'
using namespace std;
using namespace __gnu_pbds;
typedef long long ll;
typedef long double ld;
const int mod=1e9+7;
typedef tree<int,null_type,less<int>,rb_tree_tag,tree_order_statistics_node_update> ordered_set;

int main()
{
    ios_base::sync_with_stdio(0); cin.tie(0);
    
    int n, k;
    cin >> n >> k;
    vector<int> v(n);
    for(int i = 0; i < n; i++) {
        cin >> v[i];
    }   
    ll ans = 0;
    for(int i = 0; i < n; i++) {
        ll akt = 0;
        for(int j = 0; j < n; j++) {
            ll x = (ll)v[j] - k * abs(i - j);
            akt = max(akt, x);
        }
        ans += akt - v[i];
    }
    cout << ans;
    return 0;
}