// READ & UNDERSTAND
// ll, int overflow, array bounds, memset(0)
// special cases (n=1?), n+1 (1-index)
// do smth instead of nothing & stay organized
// WRITE STUFF DOWN
#include <bits/stdc++.h>
using namespace std;
#define fi first
#define se second
#define pb push_back
#define all(x) (x).begin(), (x).end()
#define MOD 1000000007
typedef long long ll;
typedef pair <int, int> ii;
typedef pair <ll, ll> pll;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef long double ld;
ll INF=LLONG_MAX;
int const mxn=404;
int dp[mxn][mxn][mxn][2]; //le,ri,cnt,where
int x[mxn],t[mxn],n,L;
int dist(int a, int b){
if(a>b)swap(a,b);
return min(b-a,L-(b-a));
}
int main()
{
ios_base::sync_with_stdio(0); cin.tie(0);
//freopen("input.txt","r",stdin); freopen("output.txt","w",stdout);
cin >> n >> L;
for(int i=0; i<n; i++){
cin >> x[i];
x[i+n+1] = x[i];
}
for(int i=0; i<n; i++){
cin >> t[i];
t[i+n+1] = t[i];
}
for(int i=0; i<=2*n; i++)
for(int j=0; j<=2*n; j++)
for(int k=0; k<=n; k++)
for(int l=0; l<2; l++)
dp[i][j][k][l]=1e9+1;
int ans = 0;
dp[n][n][0][0]=0;
for(int len=0; len<=n; len++){
for(int i=n-len; i<=n; i++){
int j=i+len;
for(int k=0; k<=n; k++){
for(int l=0; l<2; l++){
if(dp[i][j][k][l]>1e9)continue;
int pos=(l==0?i:j);
ans=max(ans,k);
if(k==n)continue;
//left
if(i){
int cur=dp[i][j][k][l]+dist(x[pos],x[i-1]);
dp[i-1][j][k+(cur<=t[i-1])][0]=min(dp[i-1][j][k+(cur<=t[i-1])][0],cur);
}
//right
if(j<2*n){
int cur=dp[i][j][k][l]+dist(x[pos],x[j+1]);
dp[i][j+1][k+(cur<=t[j+1])][1]=min(dp[i][j+1][k+(cur<=t[j+1])][1],cur);
}
}
}
}
}
cout << ans << endl;
}
