三个wa,

#include<bits/stdc++.h>
using namespace std;
int main(){
	double n,d;
	cin>>n>>d;
	int v[1000005]={},a[1000005];
	for(int i=1;i<n;i++){
		scanf("%d",&v[i]);
	}
	for(int i=1;i<=n;i++){
		scanf("%d",&a[i]);
	}
	int g=0;
	double h=0,min=100000000;
	for(int i=1;i<n;i++){
		if(a[i]<min) min=a[i];
		while(v[i]>d*h){
			h++;
			g+=min;
		} 
		h-=v[i]/d;
	}
	cout<<g;
	return 0;
}