#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
//#include<bits/extc++.h>
//__gnu_pbds
ll dpl[205][205][205];
ll dpr[205][205][205];
/*
dpl[i][j][k] = min(dpl[i+1][j][k-1]+x])
*/
int main(){
ios_base::sync_with_stdio(0),cin.tie(0),cout.tie(0);
ll n,L;
cin>>n>>L;
ll x[n+2]={0};
ll t[n+2]={0};
for(int i=1;i<=n;i++) cin>>x[i];
for(int i=1;i<=n;i++) cin>>t[i];
x[n+1]=L;
for(int l=0;l<=n+1;l++){
for(int r=0;r<=n+1;r++){
for(int k=0;k<=n;k++){
dpl[l][r][k]=1e17;
dpr[l][r][k]=1e17;
}
}
}
dpl[0][n+1][0]=0;
dpr[0][n+1][0]=0;
for(int l=0;l<n;l++){
for(int r=n+1;r>=l+2;r--){
for(int k=0;k<=n;k++){
ll ti = min(dpl[l][r][k]+x[l+1]-x[l],dpr[l][r][k]+L-x[r]+x[l+1]);
dpl[l+1][r][k+(ti<=t[l+1])] = min(dpl[l+1][r][k+(ti<=t[l+1])],ti);
ti = min(dpl[l][r][k]+L-x[r-1]+x[l],dpr[l][r][k]+x[r]-x[r-1]);
dpr[l][r-1][k+(ti<=t[r-1])] = min(dpr[l][r-1][k+(ti<=t[r-1])],ti);
}
}
}
int ans = 0;
for(int i=0;i<=n+1;i++){
for(int j=0;j<=n+1;j++){
for(int k=0;k<=n;k++){
//cout<<dpl[i][j][k]<<":"<<i<<","<<j<<","<<k<<"\n";
if(dpl[i][j][k]<1e17) ans = max(ans,k);
if(dpr[i][j][k]<1e17) ans = max(ans,k);
}
}
}
cout<<ans<<"\n";
return 0;
}
