#include <bits/stdc++.h>
using namespace std;
#define REP(i, l, r) for(int i = (l); i < (r); ++i)
#define FOR(i, l, r) for(int i = (l); i <= (r); ++i)
#define FORD(i, r, l) for(int i = (r); i >= (l); --i)
#define ff first
#define ss second
#define eb emplace_back
#define pb push_back
#define all(x) x.begin(), x.end()
#define sz(v) (int)v.size()
#define compact(v) v.erase(unique(all(v)), v.end())
#define dbg(v) "[" #v " = " << (v) << "]"
#define el "\n"
using ll = long long;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using pil = pair<int, ll>;
using pli = pair<ll, int>;
template<class T> bool minimize(T& a, const T& b){ if(a > b) return a = b, true; return false; }
template<class T> bool maximize(T& a, const T& b){ if(a < b) return a = b, true; return false; }
mt19937_64 rng(chrono::high_resolution_clock::now().time_since_epoch().count());
long long randRange(long long l, long long r){ return uniform_int_distribution<long long>(l,r)(rng); }
const int N = 205;
int n;
ll X[N], T[N], L;
ll dp[N][N][N][2]; // vis [L, R], get K stamps, 0/1 : cur_pos : L, R
ll get_dist(int l, int r) {
ll u = X[l];
ll v = X[r];
return min(v - u, L - v + u);
}
void solve() {
cin >> n >> L;
FOR(i, 1, n) cin >> X[i];
FOR(i, 1, n) cin >> T[i];
memset(dp, 0x3f, sizeof(dp));
ll inf = dp[0][0][0][0];
dp[0][n + 1][0][0] = dp[0][n + 1][0][1] = 0;
X[n + 1] = L;
FOR(l, 0, n) {
FORD(r, n + 1, l + 1) {
FORD(k, l + n + 1 - r, 0) {
FOR(dir, 0, 1) {
if (dp[l][r][k][dir] == inf) continue;
minimize(dp[l + 1][r][k][0], dp[l][r][k][dir] + (dir == 0 ? get_dist(l, l + 1) : get_dist(l + 1, r)));
minimize(dp[l][r - 1][k][1], dp[l][r][k][dir] + (dir == 0 ? get_dist(l, r - 1) : get_dist(r - 1, r)));
if (dp[l + 1][r][k][0] <= T[l + 1]) minimize(dp[l + 1][r][k + 1][0], dp[l + 1][r][k][0]);
if (dp[l][r - 1][k][1] <= T[r - 1]) minimize(dp[l][r - 1][k + 1][1], dp[l][r - 1][k][1]);
}
}
}
}
FORD(k, n, 0) {
FOR(l, 0, n) {
FOR(r, l + 1, n + 1) {
FOR(dir, 0, 1) {
if (dp[l][r][k][dir] < inf) {
cout << k << el;
return;
}
}
}
}
}
cout << 0 << el;
}
signed main() {
ios_base::sync_with_stdio(false);
cin.tie(0);
#define task "task"
if(fopen(task".inp", "r")) {
freopen(task".inp", "r", stdin);
freopen(task".out", "w", stdout);
}
solve();
return 0;
}
/*
*/
