#include<bits/stdc++.h>
using namespace std;
const int MX = 203;
const int INF = 2e9;
int n, L;
int pos[MX], T[MX];
int dp[MX][MX][MX];
int dist(int i, int j) {
int ret = abs(pos[i]-pos[j]);
return min(ret, L-ret);
}
int solve(int i, int j, int k) {
if(k==0) return dist(0, i);
if(n-(abs(j-i)-1)<k) return INF;
int &ret = dp[i][j][k];
if(ret!=-1) return ret;
ret = INF;
if(i<=j) {
if(i>1) {
if(solve(i-1, j, k-1)+dist(i, i-1)<=T[i]) {
ret = min(ret, solve(i-1, j, k-1)+dist(i, i-1));
}
if(solve(i-1, j, k)!=INF) {
ret = min(ret, solve(i-1, j, k)+dist(i, i-1));
}
} else {
if(j==n && dist(0, i)<=T[i] && k==1) {
ret = min(ret, dist(0, i));
}
}
if(j+1<=n) {
if(solve(j+1, i, k-1)+dist(j+1, i)<=T[i]) {
ret = min(ret, solve(j+1, i, k-1)+dist(j+1, i));
}
if(solve(j+1, i, k)!=INF) {
ret = min(ret, solve(j+1, i, k)+dist(j+1, i));
}
}
} else {
if(i+1<=n) {
if(solve(i+1, j, k-1)+dist(i, i+1)<=T[i]) {
ret = min(ret, solve(i+1, j, k-1)+dist(i, i+1));
}
if(solve(i+1, j, k)!=INF) {
ret = min(ret, solve(i+1, j, k)+dist(i, i+1));
}
}
if(j>1) {
if(solve(j-1, i, k-1)+dist(i, j-1)<=T[i]) {
ret = min(ret, solve(j-1, i, k-1)+dist(i, j-1));
}
if(solve(j-1, i, k)!=INF) {
ret = min(ret, solve(j-1, i, k)+dist(i, j-1));
}
} else {
if(i==n && dist(0, i)<=T[i] && k==1) {
ret = min(ret, dist(0, i));
}
}
}
return ret;
}
void PlayGround() {
cin>>n>>L;
for(int i=1; i<=n; ++i) {
cin>>pos[i];
}
for(int i=1; i<=n; ++i) {
cin>>T[i];
}
memset(dp, -1, sizeof dp);
int ans = 0;
for(int i=1; i<=n; ++i) {
for(int j=1; j<=n; ++j) {
for(int k=1; k<=n; ++k) {
if(solve(i, j, k)<INF) {
ans = max(ans, k);
}
}
}
}
cout<<ans<<'\n';
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
PlayGround();
return 0;
}
