#include <bits/stdc++.h>
#pragma GCC optimize ("Ofast", "unroll-loops")
using namespace std;
#define ll long long
#define int ll
#define FOR(i,a,b) for (int i = (a); i<(b); i++)
#define REP(i,n) FOR(i,0,n)
#define REP1(i,n) FOR(i,1,n+1)
#define RREP(i,n) for (int i=(n)-1; i>=0; i--)
#define RREP1(i,n) for (int i=(n); i>=1; i--)
#define f first
#define s second
#define pb push_back
#define ALL(x) x.begin(),x.end()
#define SZ(x) (int)(x.size())
#define SQ(x) (x)*(x)
#define pii pair<int, int>
#define pdd pair<double ,double>
#define pcc pair<char, char>
#define endl '\n'
//#define TOAD
#ifdef TOAD
#define bug(x) cerr<<__LINE__<<": "<<#x<<" is "<<x<<endl
#define IOS()
#else
#define bug(...)
#define IOS() ios::sync_with_stdio(0), cin.tie(0), cout.tie(0)
#endif
const ll inf = 1ll<<60;
const int iinf=2147483647;
const ll mod = 1e9+7;
const ll maxn=205;
const double PI=acos(-1);
ll pw(ll x, ll p, ll m=mod){
ll ret=1;
while (p>0){
if (p&1){
ret*=x;
ret%=m;
}
x*=x;
x%=m;
p>>=1;
}
return ret;
}
ll inv(ll a, ll m=mod){
return pw(a,m-2);
}
//=======================================================================================
int dp[maxn][maxn][maxn][2];
signed main (){
IOS();
int n, L; cin>>n>>L;
vector<int> t(n+2), vc(n+2);
REP1(i,n){
cin>>t[i];
}
t[n+1]=L;
REP1(i,n){
cin>>vc[i];
}
REP(i,maxn){
REP(j, maxn){
REP(k, maxn){
REP(l, 2){
dp[i][j][k][l]=inf;
}
}
}
}
dp[0][n+1][0][0]=dp[0][n+1][0][1]=0;
REP(i,n+1){
for (int j=n+1; j>i; j--){
if (i==0&&j==n+1) continue;
if (i>0) {
REP(k,maxn){
dp[i][j][k][0]=min({dp[i][j][k][0], dp[i-1][j][k][0]+t[i]-t[i-1], dp[i-1][j][k][1]+(t[i]+L-t[j])});
if (k>0){
int a=dp[i-1][j][k-1][0]+t[i]-t[i-1];
int b=dp[i-1][j][k-1][1]+(t[i]+L-t[j]);
if (a<=vc[i]) dp[i][j][k][0]=min(dp[i][j][k][0], a);
if (b<=vc[i]) dp[i][j][k][0]=min(dp[i][j][k][0], b);
}
}
}
if (j<=n) {
REP(k,maxn){
dp[i][j][k][1]=min({dp[i][j][k][1], dp[i][j+1][k][1]+t[j+1]-t[j], dp[i][j+1][k][0]+(t[i]+L-t[j])});
if (k>0){
int a=dp[i][j+1][k-1][1]+t[j+1]-t[j];
int b=dp[i][j+1][k-1][0]+(t[i]+L-t[j]);
if (a<=vc[j]) dp[i][j][k][1]=min(dp[i][j][k][1], a);
if (b<=vc[j]) dp[i][j][k][1]=min(dp[i][j][k][1], b);
}
}
}
}
}
//cout<<dp[0][3][1][1]<<endl;
//cout<<dp[0][4][1][1]<<endl;
//cout<<dp[0][4][0][1]<<endl;
int ans=0;
REP(k,maxn){
REP(i,n+1){
FOR(j,i+1,n+2){
REP(l,2){
if (dp[i][j][k][l]!=inf) ans=k;
}
}
}
}
cout<<ans<<endl;
}
