CF1218F.Workout plan

Alan decided to get in shape for the summer, so he created a precise workout plan to follow. His plan is to go to a different gym every day during the next N days and lift $X[i]$ grams on day $i$. In order to improve his workout performance at the gym, he can buy exactly one pre-workout drink at the gym he is currently in and it will improve his performance by $A$ grams permanently and immediately. In different gyms these pre-workout drinks can cost different amounts $C[i]$ because of the taste and the gym's location but its permanent workout gains are the same. Before the first day of starting his workout plan, Alan knows he can lift a maximum of $K$ grams. Help Alan spend a minimum total amount of money in order to reach his workout plan. If there is no way for him to complete his workout plan successfully output $-1$.

艾伦决定为夏天塑形，因此制定了一份精确的锻炼计划。根据该计划，他在接下来的 $N$ 天中每天前往一家不同的健身房，并在第 $i$ 天举起 $X[i]$ 克重物。为了提升自己在健身房的训练表现，他可以在当前所在的健身房恰好购买一瓶运动前饮剂，该饮剂会立即且永久地提升他的举重能力 $A$ 克。由于口味和健身房地理位置不同，各健身房中该运动前饮剂的价格 $C[i]$ 各不相同，但其带来的永久性增益效果（即 $A$ 克）始终相同。在开始锻炼计划的第一天之前，艾伦已知自己最多能举起 $K$ 克重物。请帮助艾伦计算出完成全部锻炼计划所需的最小总花费。若无法成功完成整个锻炼计划，请输出 $-1$。

The first one contains two integer numbers, integers $N$ $(1 \leq N \leq 10^5)$ and $K$ $(1 \leq K \leq 10^5)$ – representing number of days in the workout plan and how many grams he can lift before starting his workout plan respectively. The second line contains $N$ integer numbers $X[i]$ $(1 \leq X[i] \leq 10^9)$ separated by a single space representing how many grams Alan wants to lift on day $i$. The third line contains one integer number $A$ $(1 \leq A \leq 10^9)$ representing permanent performance gains from a single drink. The last line contains $N$ integer numbers $C[i]$ $(1 \leq C[i] \leq 10^9)$ , representing cost of performance booster drink in the gym he visits on day $i$.

第一行包含两个整数 $N$（$1 \leq N \leq 10^5$）和 $K$（$1 \leq K \leq 10^5$），分别表示训练计划的天数以及 Alan 在开始训练计划前能举起的重量（单位：克）。
第二行包含 $N$ 个整数 $X[i]$（$1 \leq X[i] \leq 10^9$），以单个空格分隔，表示 Alan 在第 $i$ 天希望举起的重量（单位：克）。
第三行包含一个整数 $A$（$1 \leq A \leq 10^9$），表示每次饮用性能增强饮料所带来的永久性能力提升（单位：克）。
最后一行包含 $N$ 个整数 $C[i]$（$1 \leq C[i] \leq 10^9$），表示 Alan 在第 $i$ 天所访问的健身房中性能增强饮料的价格。

One integer number representing minimal money spent to finish his workout plan. If he cannot finish his workout plan, output -1.

一个整数，表示完成训练计划所需的最少花费。如果无法完成训练计划，则输出 -1。

First example: After buying drinks on days 2 and 4 Alan can finish his workout plan. Second example: Alan cannot lift 40000 grams on day 2.

第一个例子：艾伦在第 2 天和第 4 天购买饮料后，可以完成他的健身计划。
第二个例子：艾伦在第 2 天无法举起 40000 克的重量。