#include <bits/stdc++.h>
#define ll long long
#define mod 998244353
using namespace std;
const int N=205;
int n,m,k,s,t,L,SUM[N];
int f[N][N][N][2];//f[i][j][k] 左边走了i步，右边走了j步，拿到k个雕像，最少时间 
struct node{
	int x,t;
}a[N];
void cmin(int &a,int b){
	a=min(a,b);
}
int main(){  
//	freopen("in.txt","r",stdin);
	cin>>n>>L;
	memset(f,0x3f,sizeof(f));
	f[0][0][0][0]=0; 
	for (int i=1;i<=n;++i) cin>>a[i].x;
	for (int i=1;i<=n;++i) cin>>a[i].t;
	for (int i=1;i<=n;++i) SUM[i]=L-a[n-i+1].x;
	for (int i=0;i<=n;++i)
		for (int j=0;i+j<n;++j)
			for (int k=0;k<=i+j;++k){
				if (f[i][j][k][0]<0x3f3f3f3f){
					cmin(f[i+1][j][k+(f[i][j][k][0]+a[i+1].x-a[i].x<=a[i+1].t)][0],f[i][j][k][0]+a[i+1].x-a[i].x);
					cmin(f[i][j+1][k+(f[i][j][k][0]+a[i].x+SUM[j+1]<=a[n-j].t)][1],f[i][j][k][0]+a[i].x+SUM[j+1]);
				}
				if (f[i][j][k][1]<0x3f3f3f3f){
					cmin(f[i][j+1][k+(f[i][j][k][1]+a[n-j+1].x-a[n-j].x<=a[n-j].t)][1],f[i][j][k][1]+a[n-j+1].x-a[n-j].x);
					cmin(f[i+1][j][k+(f[i][j][k][1]+SUM[j]+a[i+1].x<=a[i+1].t)][0],f[i][j][k][1]+SUM[j]+a[i+1].x);
				}
			}
	int ans=0;
	for (int i=0;i<=n;++i)
		for (int k=0;k<=n;++k)
			if (f[i][n-i][k][0]<0x3f3f3f3f || f[i][n-i][k][1]<0x3f3f3f3f)
				ans=max(ans,k);
	cout<<ans;
}