#include<bits/stdc++.h>
#define fi first
#define se second
#define int long long
using namespace std;
using ll = long long;
using ii = pair<int, int>;
using aa = array<int,3>;
const int N = 1e5;
const int INF = 1e9;
int dp[205][205][205][2];
int a[205];
int ti[205];
int n,l;
int dist(int x,int y) {
if(x<y) swap(x,y);
return min(x-y,l-x+y);
}
int get(int x,int y) {
if(x+y>n) return (x+y)%n;
return x+y;
}
void solve(int i,int j,int k) {
int t=get(i+1,j-2);
int cur=get(i,1);
int tmp=min(dp[cur][j-1][k][0]+dist(a[i],a[cur]),dp[cur][j-1][k][1]+dist(a[i],a[t]));
if(dp[i][j][k][0]>ti[i] && tmp<=ti[i]) {
dp[i][j][k+1][0]=tmp;
}
//cout << dp[i][j][k+1][0] << endl;
dp[i][j][k][0]=min(dp[i][j][k][0],tmp);
t=get(i,j-2);
cur=get(i,j-1);
tmp=min(dp[i][j-1][k][0]+dist(a[i],a[cur]),dp[i][j-1][k][1]+dist(a[t],a[cur]));
if(dp[i][j][k][1]>ti[cur] && tmp<=ti[cur]) {
dp[i][j][k+1][1]=tmp;
}
//cout << dp[i][j][k+1][1] << ' ' << tmp << end;
dp[i][j][k][1]=min(dp[i][j][k][1],tmp);
}
signed main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cin >> n >> l;
for(int i=1;i<=n;i++) {
cin >> a[i];
}
for(int i=1;i<=n;i++) {
cin >> ti[i];
}
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]=dp[i][j][k][1]=1e18;
}
}
if(1) {
bool x=(min(l-a[1],a[1])<=ti[1]);
dp[1][1][x][0]=min(n-a[1],a[1]);
dp[1][1][x][1]=min(n-a[1],a[1]);
x=(min(l-a[n],a[n])<=ti[n]);
dp[n][1][x][0]=min(l-a[n],a[n]);
dp[n][1][x][1]=min(l-a[n],a[n]);
}
int ans=0;
for(int j=2;j<=n;j++) {
for(int i=1;i<=n;i++) {
for(int k=j;k>=0;k--) {
solve(i,j,k);
}
for(int k=0;k<=j;k++) {
if(j==n && min(dp[i][j][k][0],dp[i][j][k][1])<1e18) {
ans=max(ans,k);
}
}
}
}
solve(5,2,1);
cout << ans;
return 0;
}
