#include <iostream>
#include <math.h>
#include <vector>
#include <queue>
#include <algorithm>
using namespace std;
struct State{
int l, r, res, t, side;
bool first;
};
int GetDiff(int a, int b, int l, int side){
if ((a<b&&side==1)||(a>b&&side==-1)) return abs(a-b);
if (a<b) return a+l-b;
return b+l-a;
}
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int n, l;
cin>>n>>l;
vector<int> positions(n), times(n);
for (int i=0;i<n;i++) cin>>positions[i];
for (int i=0;i<n;i++) cin>>times[i];
queue<State> q;
q.push({0, 0, (times[0]>=positions[0]?1:0), positions[0], 1, true});
q.push({n-1, n-1, (times[n-1]>=l-positions[n-1]?1:0), l-positions[n-1], -1, true});
int out=0;
while (!q.empty()){
State sta1=q.front();
q.pop();
if (sta1.res==n){
cout<<n<<'\n';
return 0;
}
out=max(out, sta1.res);
if (sta1.t>l*2+1||(sta1.l==sta1.r&&!sta1.first)) continue;
sta1.first=false;
State sta2=sta1;
int pos=(sta1.side==1?sta1.r:sta1.l);
sta1.r++;
sta1.r%=n;
sta1.t+=GetDiff(positions[pos], positions[sta1.r], l, 1);
if (times[sta1.r]>=sta1.t) sta1.res++;
sta2.l--;
if (sta2.l<0) sta2.l+=n;
sta2.t+=GetDiff(positions[pos], positions[sta2.l], l, -1);
if (times[sta2.l]>=sta2.t) sta2.res++;
q.push(sta1);
q.push(sta2);
}
cout<<out<<'\n';
return 0;
}
