#include <iostream>
#include <complex>
#include <vector>
#include <string>
#include <algorithm>
#include <cstdio>
#include <numeric>
#include <cstring>
#include <ctime>
#include <cstdlib>
#include <set>
#include <map>
#include <unordered_map>
#include <unordered_set>
#include <list>
#include <cmath>
#include <bitset>
#include <cassert>
#include <queue>
#include <stack>
#include <deque>
#include <random>
using namespace std;
template<typename T1, typename T2> inline void chkmin(T1 &a, T2 b) {if (a > b) a = b;}
template<typename T1, typename T2> inline void chkmax(T1 &a, T2 b) {if (a < b) a = b;}
#define files(FILENAME) read(FILENAME); write(FILENAME)
#define read(FILENAME) freopen((FILENAME + ".in").c_str(), "r", stdin)
#define write(FILENAME) freopen((FILENAME + ".out").c_str(), "w", stdout)
#define all(c) (c).begin(), (c).end()
#define sz(c) (int)(c).size()
#define left left228
#define right right228
#define y1 y1228
#define mp make_pair
#define pb push_back
#define y2 y2228
#define rank rank228
using ll = long long;
using ld = long double;
const string FILENAME = "input";
const int MAXN = 228;
int n, l;
ll x[MAXN], t[MAXN];
ll dp[MAXN][MAXN][2][MAXN];
int dist(int i, int j) {
return min(abs(x[i] - x[j]), l - abs(x[i] - x[j]));
}
ll solve(int l, int r, int side, int cnt) {
if (cnt == 0) {
return (1LL << 60);
}
if (l > r) {
return -(1LL << 60);
}
if (dp[l][r][side][cnt] != -1) {
return dp[l][r][side][cnt];
}
int pos;
if (side == 0) {
pos = l - 1;
} else {
pos = r + 1;
}
ll ans = -(1LL << 60);
chkmax(ans, solve(l + 1, r, 0, cnt) - dist(l, pos));
chkmax(ans, min(t[l], solve(l + 1, r, 0, cnt - 1)) - dist(l, pos));
chkmax(ans, solve(l, r - 1, 1, cnt) - dist(r, pos));
chkmax(ans, min(t[r], solve(l, r - 1, 1, cnt - 1)) - dist(r, pos));
dp[l][r][side][cnt] = ans;
return dp[l][r][side][cnt];
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
//read(FILENAME);
cin >> n >> l;
for (int i = 0; i < n; i++) {
cin >> x[i];
}
for (int i = 0; i < n; i++) {
cin >> t[i];
}
memset(dp, -1, sizeof(dp));
ll sol = 0;
for (int i = 0; i <= n; i++) {
if (solve(0, n - 1, 1, i) >= 0) {
sol = i;
}
}
cout << sol << '\n';
return 0;
}
