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#include <cstdio>
#include <cmath>
#include <iostream>
#include <algorithm>
#include <queue>
#include <list>
#include <vector>
#include <map>
#include <unordered_map>
#include <unordered_set>
#include <set>
#include <bitset>
#include <stack>
#include <string>
#include <cstring>
#include <cassert>
#include <limits.h>

using namespace std;

typedef long long LL;
typedef long double LD;

typedef vector<int> VI;
#define REP(i,n) for(int i=0;i<(n);i++)
#define FOR(i,a,b) for(VAR(i,a);i<=(b);++i)
#define FORD(i,a,b) for(VAR(i,a);i>=(b);--i)
#define FORE(a,b) for(VAR(a,(b).begin());a!=(b).end();++a)
#define VAR(a,b) __typeof(b) a=(b)
#define SIZE(a) ((int)((a).size()))
#define ALL(x) (x).begin(),(x).end()
#define CLR(x,a) memset(x,a,sizeof(x))
#define ZERO(x) memset(x,0,sizeof(x))
#define S(t,i) scanf("%" ## t, &i)
#define SI(i) scanf("%d", &i)

const int MAXN=1000+11;
int n, k;
struct node {
    int x;
    int h;

    bool operator<(const node& other) const {
        return h < other.h;
    }
};

priority_queue<node> q;
int h[MAXN];
LL ans;

int main() {
    ios_base::sync_with_stdio(0);
    cin >> n >> k;
    REP(ni, n) {
        cin >> h[ni];
        q.push({ni, h[ni]});
    }
    while (!q.empty()) {
        node cn = q.top();
        q.pop();
        //cout << cn.x << " " <<cn.h<< "\n";
        if (cn.x-1>=0 && abs(h[cn.x-1]-h[cn.x])>k) {
            int diff = max(abs(h[cn.x-1]-h[cn.x])-k, 0);
            ans+=diff;
            h[cn.x-1] += diff;
            q.push({cn.x-1, h[cn.x-1]});
        }

        if (cn.x+1<= n-1 && abs(h[cn.x+1]-h[cn.x])>k) {
            int diff = max(abs(h[cn.x+1]-h[cn.x])-k, 0);
            ans+=diff;
            h[cn.x+1] += diff;
            q.push({cn.x+1, h[cn.x+1]});
        }
    }

    cout << ans << "\n";
    return 0;
}