#include <bits/stdc++.h>
using namespace std;
#define lalala ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
#define N 205
#define pb push_back
#define int long long int
#define s second
#define big 1000000000000
int arr[N][2],ters[N][2];
int n,k;
int dp[N][N][N][2];//clockwise ,anticlockwise, kaç_aldım, nerdeydim=min tim
signed main(){
lalala;
cin>>n>>k;
for(int i=1;i<=n;i++)cin>>arr[i][0];
for(int i=1;i<=n;i++)cin>>arr[i][1];
for(int i=0;i<=n;i++){
for(int j=0;j<=n;j++){
for(int k=0;k<=n;k++){
dp[i][j][k][0]=big;
dp[i][j][k][1]=big;
}
}
}
dp[0][0][0][1]=0;
dp[0][0][0][0]=0;
arr[n+1][0]=k;
//kac==0;precomputeÜ
for(int i=0;i<=n;i++){
for(int j=0;j<=n;j++){
int b=n-j-1;
if(i==0&&j==0)continue;
dp[i][j][0][1]=k-arr[b][0]+2*arr[i][0];
dp[i][j][0][0]=(k-arr[b][0])*2+arr[i][0];
}
}
for(int co=0;co<=n;co++){
for(int anti=0;anti<=n;anti++){
if(anti+co>n)break;
for(int kac=1;kac<=co+anti;kac++){
if(co==0&&anti==0)break;
int yer=n-anti+1;
//cout<<co<<" "<<anti<<" "<<kac<<" "<<yer<<endl;
if(co){
//0 dayim
int uzak=(arr[co][0]-arr[co-1][0]);
dp[co][anti][kac][0]=dp[co-1][anti][kac][0]+uzak;
int a=dp[co-1][anti][kac-1][0]+uzak;
if(a<=arr[co][1])dp[co][anti][kac][0]=min(dp[co][anti][kac][0],a);
uzak=(arr[co][0]+k-arr[yer][0]);
dp[co][anti][kac][0]=min(dp[co][anti][kac][0], dp[co-1][anti][kac][1]+uzak);
a=dp[co-1][anti][kac-1][1]+uzak;
if(a<=arr[co][1])dp[co][anti][kac][0]=min(dp[co][anti][kac][0],a);
}
if(yer<=n){
//1deyim
int uzak=abs(arr[yer][0]-arr[yer+1][0]);
dp[co][anti][kac][1]=dp[co][anti-1][kac][1]+uzak;
int a=dp[co][anti-1][kac-1][1]+uzak;
if(a<=arr[yer][1])dp[co][anti][kac][1]=min(dp[co][anti][kac][1],a);
uzak=(arr[co][0]+k-arr[yer][0]);
dp[co][anti][kac][1]=min(dp[co][anti][kac][1], dp[co][anti-1][kac][0]+uzak);
a=dp[co][anti-1][kac-1][0]+uzak;
if(a<=arr[yer][1])dp[co][anti][kac][0]=min(dp[co][anti][kac][0],a);
//cout<<dp[co][anti][kac][1]<<" ! "<<uzak<<endl<<endl;
}
}
}
}
int ans=0;
for(int i=0;i<=n;i++){
for(int j=0;j<=n;j++){
for(int k=0;k<=n;k++){
if(dp[i][j][k][0]<big)ans=max(ans,k);
if(dp[i][j][k][1]<big)ans=max(ans,k);
}
}
}cout<<ans<<endl;
}
