#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pll pair<ll,ll>
#define fs first
#define sc second
const ll mxn = 202;
ll dp[mxn][mxn][mxn][2];
bool done[mxn][mxn][mxn][2];
pll arr[mxn];
priority_queue<tuple<ll,ll,ll,ll,ll>,vector<tuple<ll,ll,ll,ll,ll>>,greater<tuple<ll,ll,ll,ll,ll>>> pq;
ll n,L;
const ll inf = 1e9+10;
ll calc(ll s,ll e,ll dir){
if(dir){
return (e+L-s)%(L);
}
else{
return L-(e+L-s)%L;
}
}
void solve(){
cin>>n>>L;
for(int i = 1;i<=n;i++)cin>>arr[i].fs;
for(int i = 1;i<=n;i++)cin>>arr[i].sc;
for(auto &i:dp)for(auto &j:i)for(auto &k:j)for(auto &l:k)l = inf;
arr[0] = {0,0};
dp[0][0][0][0] = 0;
pq.push(make_tuple(0,0,0,0,0));
ll ans = 0;
while(!pq.empty()){
ll val = get<0>(pq.top()),l = get<1>(pq.top()),r = get<2>(pq.top());
ll cnt = get<3>(pq.top()),dir = get<4>(pq.top());
//cout<<val<<' '<<l<<' '<<r<<' '<<cnt<<' '<<dir<<endl;
pq.pop();
if(dp[l][r][cnt][dir] != val)continue;
if((r+1)%(n+1) == l){
ans = max(ans,cnt);
continue;
}
ll pos = (dir?arr[r].fs:arr[l].fs);
int nr = r+1;
if(nr>=n+1)nr -= n+1;
int nl = l-1;
if(nl<0)nl += n+1;
ll rt = val+calc(pos,arr[nr].fs,1);
ll rcnt = cnt + (rt<=arr[nr].sc?1:0);
if(dp[l][nr][rcnt][1] > rt)pq.push(make_tuple(rt,l,nr,rcnt,1)),dp[l][nr][rcnt][1] = rt;
ll lt = val+calc(pos,arr[nl].fs,0);
ll lcnt = cnt+(lt<=arr[nl].sc?1:0);
//cout<<l<<','<<r<<','<<dir<<','<<pos<<lt<<','<<lcnt<<','<<','<<nl<<endl;
if(dp[nl][r][lcnt][0] > lt)pq.push(make_tuple(lt,nl,r,lcnt,0)),dp[nl][r][lcnt][0] = lt;
}
cout<<ans;
}
int main(){
ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
int t = 1;
while(t--)solve();
}
