#include <bits/stdc++.h>
using namespace std;
#define int long long
#define double long double
#define FOR(i, l, r, d) for(int i=(l); i<=(r); i+=(d))
#define szof(x) ((int)(x).size())
#define vi vector<int>
#define pii pair<int, int>
#define F first
#define S second
#define pb push_back
#define eb emplace_back
#define mkp make_pair
const int INF = INT_MAX;
const int LNF = INF*INF;
const int MOD = 1000000007;
const double eps = 1e-12;
// #pragma GCC optimize("Ofast")
// #pragma GCC optimize("unroll-loops")
const int MAX = 210;
int n, L;
int pos[MAX];
int lim[MAX];
int dp[MAX][MAX][MAX][2];
// dp[l][r][c][p] : min. time of visited l from left, r from right, collected c, now at l/r
signed main(){
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
cin>>n>>L;
FOR(i, 1, n, 1){
cin>>pos[i];
}
pos[n+1] = L;
FOR(i, 1, n, 1){
cin>>lim[i];
}
FOR(l, 0, n, 1){
FOR(r, 0, n, 1){
FOR(c, 0, n, 1){
FOR(p, 0, 1, 1){
dp[l][r][c][p] = LNF;
}
}
}
}
dp[0][0][0][0] = dp[0][0][0][1] = 0;
FOR(l, 0, n, 1){
FOR(r, 0, n, 1){
if(l + r >= n) break;
FOR(c, 0, n, 1){
// dp[l][r][c][0] -> dp[l+1][r][?][0], dp[l][r+1][?][1]
int tol = dp[l][r][c][0] + (pos[l+1] - pos[l]);
int tor = dp[l][r][c][0] + (pos[l] + L - pos[n-r]);
int cl = c + (tol <= lim[l+1]);
int cr = c + (tor <= lim[n-r]);
dp[l+1][r][cl][0] = min(dp[l+1][r][cl][0], tol);
dp[l][r+1][cr][1] = min(dp[l][r+1][cr][1], tor);
// dp[l][r][c][1] -> dp[l+1][r][?][0], dp[l][r+1][?][1]
tol = dp[l][r][c][1] + (L - pos[n-r+1] + pos[l+1]);
tor = dp[l][r][c][1] + (pos[n-r+1] - pos[n-r]);
cl = c + (tol <= lim[l+1]);
cr = c + (tor <= lim[n-r]);
dp[l+1][r][cl][0] = min(dp[l+1][r][cl][0], tol);
dp[l][r+1][cr][1] = min(dp[l][r+1][cr][1], tor);
}
}
}
int res = 0;
FOR(l, 0, n, 1){
FOR(r, 0, n, 1){
FOR(c, 0, n, 1){
FOR(p, 0, 1, 1){
if(dp[l][r][c][p] < LNF) res = max(res, c);
}
}
}
}
cout<<res<<'\n';
return 0;
}
