#include <bits/stdc++.h>
#pragma GCC optimize ("O2,unroll-loops")
//#pragma GCC optimize("no-stack-protector,fast-math")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<pii, int> piii;
typedef pair<ll, ll> pll;
#define debug(x) cerr<<#x<<'='<<(x)<<endl;
#define debugp(x) cerr<<#x<<"= {"<<(x.first)<<", "<<(x.second)<<"}"<<endl;
#define debug2(x, y) cerr<<"{"<<#x<<", "<<#y<<"} = {"<<(x)<<", "<<(y)<<"}"<<endl;
#define debugv(v) {cerr<<#v<<" : ";for (auto x:v) cerr<<x<<' ';cerr<<endl;}
#define all(x) x.begin(), x.end()
#define pb push_back
#define upd(x, y) x=min(x, y);
const ld eps=1e-7;
const int inf=1000000010;
const ll INF=10000000000000010LL;
const int mod=1000000007;
const int N=205;
int n, m, k, u, v, x, y, t, a, b, ans;
int X[N], T[N], L;
int dp0[N][N][N];
int dp1[N][N][N];
int main(){
ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
//freopen("input.txt", "r", stdin);
//freopen("output.txt", "w", stdout);
cin>>n>>L;
for (int i=1; i<=n; i++) cin>>X[i];
for (int i=1; i<=n; i++) cin>>T[i];
X[n+1]=L;
memset(dp0, 63, sizeof(dp0));
memset(dp1, 63, sizeof(dp1));
dp0[0][0][0]=0;
for (int x=0; x<n; x++) for (int y=0; x+y<n; y++) for (int k=0; k<=x+y; k++){
if (dp0[x][y][k]<inf){
int t=dp0[x][y][k] + X[x+1]-X[x];
upd(dp0[x+1][y][k+(T[x+1]>=t)], t);
t=dp0[x][y][k] + X[x]+L-X[n-y];
upd(dp1[x][y+1][k+(T[n-y]>=t)], t);
}
if (dp1[x][y][k]<inf){
// cerr<<"upd "<<x<<' '<<y<<' '<<k<<endl;
int t=dp1[x][y][k] + X[n-y+1]-X[n-y];
upd(dp1[x][y+1][k+(T[n-y]>=t)], t);
t=dp1[x][y][k] + L-X[n-y+1]+X[x+1];
// debug(t)
upd(dp0[x+1][y][k+(T[x+1]>=t)], t);
}
}
for (int x=0; x<=n; x++) for (int y=0; x+y<=n; y++) for (int k=0; k<=x+y; k++)
if (min(dp0[x][y][k], dp1[x][y][k])<inf) ans=max(ans, k);
cout<<ans<<'\n';
// debug(dp1[0][1][1])
// debug(dp1[0][2][2])
// debug(dp0[1][2][3])
return 0;
}
