#include <bits/stdc++.h>
#define int long long
#define ff first
#define ss second
#define pb push_back
#define all(x) x.begin(),x.end()
using namespace std;
const int N=205;
int dp[N][N][N][2],a[N],b[N];
signed main(){
ios_base::sync_with_stdio();
cin.tie(0);cout.tie(0);
int n,L;
cin>>n>>L;
for(int i=1;i<=n;i++)cin>>a[i];
for(int i=1;i<=n;i++)cin>>b[i];
for(int i=0;i<=n+1;i++){
for(int j=0;j<=n+1;j++){
for(int k=0;k<=n;k++){
dp[i][j][k][0]=1e18;
dp[i][j][k][1]=1e18;
}
}
}
a[n+1]=L;
dp[0][n+1][0][0]=0;
dp[0][n+1][0][1]=0;
for(int l=0;l<=n;l++){
for(int r=n+1;r>l;r--){
for(int k=0;k<=n;k++){
int x=dp[l][r][k][0]+a[l+1]-a[l];
if(x<=b[l+1])dp[l+1][r][k+1][0]=min(dp[l+1][r][k+1][0],x);
else dp[l+1][r][k][0]=min(dp[l+1][r][k][0],x);
x=dp[l][r][k][1]+L-(a[r]-a[l+1]);
if(x<=b[l+1])dp[l+1][r][k+1][0]=min(dp[l+1][r][k+1][0],x);
else dp[l+1][r][k][0]=min(dp[l+1][r][k][0],x);
x=dp[l][r][k][1]+a[r]-a[r-1];
if(x<=b[r-1])dp[l][r-1][k+1][1]=min(dp[l][r-1][k+1][1],x);
else dp[l][r-1][k][1]=min(dp[l][r-1][k][1],x);
x=dp[l][r][k][0]+L-(a[r-1]-a[l]);
if(x<=b[r-1])dp[l][r-1][k+1][1]=min(dp[l][r-1][k+1][1],x);
else dp[l][r-1][k][1]=min(dp[l][r-1][k][1],x);
}
}
}
int ans=0;
for(int l=0;l<=n;l++){
for(int r=n+1;r>l;r--){
for(int k=0;k<=n;k++){
if(dp[l][r][k][0]!=1e18)ans=max(ans,k);
if(dp[l][r][k][1]!=1e18)ans=max(ans,k);
}
}
}
cout<<ans<<"\n";
}
/*
*/
