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#include <iostream>
#include <set>

using namespace std;

const int maxN=1e3;

int n, k, arr[maxN];
long long result=0;
set<pair<int, int>>S;


void flood_fill(int crr){
    S.erase({arr[crr], crr});
    for(int i=crr-1; i>=0; i--){
        if(arr[i]-arr[i+1] > k)break;
        S.erase({arr[i], i});
        if(arr[i+1]-arr[i] > k){
            int inc = arr[i+1]-k-arr[i];
            arr[i] += inc;
            result += inc;
        }
    }
    for(int i=crr+1; i<n; i++){
        if(arr[i]-arr[i-1] > k)break;
        S.erase({arr[i], i});
        if(arr[i-1]-arr[i] > k){
            int inc = arr[i-1]-k-arr[i];
            arr[i] += inc;
            result += inc;
        }
    }
}

int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cin>>n>>k;
    for(int i=0; i<n; i++){
        cin>>arr[i];
        S.insert({arr[i], i});
    }
    while(!S.empty())flood_fill(S.rbegin()->second);
    cout<<result;
    return 0;
}