#include <bits/stdc++.h>
using namespace std;
#define int long long
#define inf (long long)(1e15)
signed main(){
cin.tie(0);
ios_base::sync_with_stdio(0);
//start here
int N,L;
cin >> N >> L;
vector<int> X(N+1,0);
vector<int> T(N+1,0);
for(int i = 1;i <= N;i++)cin >> X[i];
for(int i = 1;i <= N;i++)cin >> T[i];
vector dp(N+1,vector(N+1,vector(N+1,vector<int>(2,inf))));// dp[a][b][cnt][counter_clockwise/clockwise]
dp[0][0][0][0] = 0;
dp[0][0][0][1] = 0;
for(int len = 1;len <= N;len++){
for(int a = 0;a <= N;a++){//current at a
for(int cnt = 0;cnt <= N;cnt++){
for(int clock = 0;clock <= 1;clock++){
int b;
if(clock == 1){
b = (a+(len-1))%(N+1);
}else{
b = (a-(len-1)+N+1)%(N+1);
}
if(dp[a][b][cnt][clock] == inf)continue;
int ctime = dp[a][b][cnt][clock];
// go to a-1
if(clock){// clockwise(1)
int nxtA = (a-1+N+1)%(N+1);
int nxtB = (b+1)%(N+1);
if(nxtA == b)continue;
{
int ntime = ctime+min(abs(X[nxtA]-X[a]),L-abs(X[nxtA]-X[a]));
dp[nxtA][b][cnt+(ntime <= T[nxtA])][1] =
min(dp[nxtA][b][cnt+(ntime <= T[nxtA])][1],ntime);
}
// go to other+1
{
int ntime = ctime+min(abs(X[nxtB]-X[a]),L-abs(X[nxtB]-X[a]));
dp[nxtB][a][cnt+(ntime <= T[nxtB])][0] =
min(dp[nxtB][a][cnt+(ntime <= T[nxtB])][0],ntime);
}
}else{//counter clockwise
int nxtA = (a+1)%(N+1);
int nxtB = (b-1+N+1)%(N+1);
if(nxtA == b)continue;
// go to nxtA
{
int ntime = ctime+min(abs(X[nxtA]-X[a]),L-abs(X[nxtA]-X[a]));
dp[nxtA][b][cnt+(ntime <= T[nxtA])][0] =
min(dp[nxtA][b][cnt+(ntime <= T[nxtA])][0],ntime);
}
// go to nxtB
{
int ntime = ctime+min(abs(X[nxtB]-X[a]),L-abs(X[nxtB]-X[a]));
dp[nxtB][a][cnt+(ntime <= T[nxtB])][1] =
min(dp[nxtB][a][cnt+(ntime <= T[nxtB])][1],ntime);
}
}
}
}
}
}
for(int cnt = N;cnt >= 0;cnt--){
for(int a = 0;a <= N;a++){
for(int b = 0;b <= N;b++){
for(int clock = 0;clock <= 1;clock++){
if(dp[a][b][cnt][clock] == inf)continue;
cout << cnt << '\n';
return 0;
}
}
}
}
}
