#include <bits/stdc++.h>
using namespace std;
#define int long long
#define pll pair<int, int>
#define mp make_pair
#define pb push_back
#define f first
#define s second
#define endl '\n'
#define ld long double
#define sz(x) static_cast<int>((x).size())
void chmin(int & x, int v) {
x=min(x, v);
}
signed main(){
int n,m;cin>>n>>m;
vector<int> x(n+4,0), t(n+4,0);
for(int i=2;i<=n+1;i++)cin>>x[i];
for(int i=2;i<=n+1;i++)cin>>t[i];
int mem[n+4][n+4][n+4][2];
for(int i=0;i<n+4;i++) for(int j=0;j<n+4;j++) for(int k=0;k<n+4;k++) mem[i][j][k][0]=mem[i][j][k][1]=1e15;
mem[1][1][n+2][0]=mem[1][1][n+2][1]=0;
auto dist=[&](int a, int b)->int{
return min(m-abs(x[a]-x[b]), abs(x[a]-x[b]));
};
int ans=0;
for(int i=1;i<=n+1;i++){
for(int j=1;j<=n+2;j++){
for(int k=n+2;k>j;k--){
// right to right
if(mem[i-1][j][k+1][1]+dist(k+1, k) <= t[k])
chmin(mem[i][j][k][1], mem[i-1][j][k+1][1]+dist(k+1, k));
chmin(mem[i][j][k][1],mem[i][j][k+1][1]+dist(k+1, k));
//left to right
if(mem[i-1][j][k+1][0]+dist(j, k)<=t[k])
chmin(mem[i][j][k][1], mem[i-1][j][k+1][0]+dist(j,k));
chmin(mem[i][j][k][1], mem[i][j][k+1][0]+dist(j, k));
// left to left
if(mem[i-1][j-1][k][0]+dist(j-1, j) <= t[j])
chmin(mem[i][j][k][0], mem[i-1][j-1][k][0]+dist(j-1, j));
chmin(mem[i][j][k][0], mem[i][j-1][k][0]+dist(j-1, j));
// right to left
if(mem[i-1][j-1][k][1]+dist(j, k)<=t[j])
chmin(mem[i][j][k][0], mem[i-1][j-1][k][1]+dist(j, k));
//~ if(i==3 and j==2 and k==4){
//~ printf("coming from %lld, dist %lld\n", mem[i-1][j-1][k][1], dist(j, k));
//~ }
chmin(mem[i][j][k][0], mem[i][j-1][k][1]+dist(j, k));
chmin(mem[i][j][k][1], mem[i][j][k][0]+dist(j, k));
chmin(mem[i][j][k][0], mem[i][j][k][1]+dist(j, k));
if(mem[i][j][k][0] < 1e12 or mem[i][j][k][1] < 1e12) ans=i;
//~ printf("i %lld, l(j) %lld, r(k) %lld, 0: %lld, 1: %lld\n", i,j,k,mem[i][j][k][0],mem[i][j][k][1]);
}
}
}
cout<<ans-1;
}
/*
3 5
1 2 3
1 2 3
4 10
1 2 8 9
5 6 2 1
6 10
1 2 3 4 5
1 2 3 4 5
6 87
9 23 44 62 67 78
15 91 53 91 89 46
*/
