#include <iostream>
#include <iomanip>
#include <algorithm>
#include <numeric>
#include <cmath>
#include <cassert>
#include <ctime>
#include <chrono>
#include <cstdio>
#include <random>
#include <vector>
#include <string>
#include <map>
#include <unordered_map>
#include <set>
#include <unordered_set>
#include <deque>
#include <queue>
#include <bitset>
#include <list>
#include <fstream>
#include <functional>
#include <complex>
using namespace std;
mt19937_64 rnd(chrono::steady_clock::now().time_since_epoch().count());
short skip_cin = 0;
const long long INF = 1e18, MOD = 1e9 + 7, MOD2 = 998244353, LOG = 18;
const long double EPS = 1e-9, PI = acos(-1);
const long long N = 205;
long long n, l;
vector<long long> x, t;
long long dp[N][N][N][2];
void solve()
{
for (long long left = 0; left < N; left++)
{
for (long long right = 0; right < N; right++)
{
for (long long hv = 0; hv < N; hv++)
{
for (long long lr = 0; lr < 2; lr++)
{
dp[left][right][hv][lr] = INF;
}
}
}
}
cin >> n >> l;
x.resize(n + 2);
x[0] = 0;
for (long long i = 1; i < n + 1; i++)
{
cin >> x[i];
}
x[n + 1] = l;
t.resize(n + 2);
t[0] = INF;
for (long long i = 1; i < n + 1; i++)
{
cin >> t[i];
}
t[n + 1] = INF;
n += 2;
dp[1][1][2][0] = 0;
for (long long sum = 2; sum < n; sum++)
{
for (long long left = 1; left < n + 1; left++)
{
long long right = sum - left;
long long lidx = left - 1, ridx = n - right;
if (right <= 0)
{
break;
}
for (long long hv = 2; hv < left + right + 1; hv++)
{
long long tol = x[lidx + 1] - x[lidx];
long long add = (dp[left][right][hv][0] + tol <= t[lidx + 1]);
dp[left + 1][right][hv + add][0] = min(dp[left + 1][right][hv + add][0], dp[left][right][hv][0] + tol);
long long tor = l - (x[ridx - 1] - x[lidx]);
add = (dp[left][right][hv][0] + tor <= t[ridx - 1]);
dp[left][right + 1][hv + add][1] = min(dp[left][right + 1][hv + add][1], dp[left][right][hv][0] + tor);
tor = x[ridx] - x[ridx - 1];
add = (dp[left][right][hv][1] + tor <= t[ridx - 1]);
dp[left][right + 1][hv + add][1] = min(dp[left][right + 1][hv + add][1], dp[left][right][hv][1] + tor);
tol = l - (x[ridx] - x[lidx + 1]);
add = (dp[left][right][hv][1] + tol <= t[lidx + 1]);
dp[left + 1][right][hv + add][0] = min(dp[left + 1][right][hv + add][0], dp[left][right][hv][1] + tol);
}
}
}
long long ans = 0;
for (long long left = 0; left < n + 1; left++)
{
for (long long right = 0; right < n + 1; right++)
{
for (long long hv = 0; hv < n + 1; hv++)
{
for (long long lr = 0; lr < 2; lr++)
{
if (dp[left][right][hv][lr] != INF)
{
ans = max(ans, hv);
}
}
}
}
}
ans -= 2;
cout << ans << "\n";
}
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
srand(time(NULL));
int tst = 1;
//cin >> tst;
while (tst--)
{
solve();
}
return 0;
}
/*
<3 <3 <3 <3 <3 <3 <3 <3 <3 <3 <3 <3 <3
⠀⠀⠀⠀⠀⠀⠀⠀⠀⣠⠤⠖⠚⢉⣩⣭⡭⠛⠓⠲⠦⣄⡀⠀⠀⠀⠀⠀⠀⠀
⠀⠀⠀⠀⠀⠀⢀⡴⠋⠁⠀⠀⠊⠀⠀⠀⠀⠀⠀⠀⠀⠀⠉⠳⢦⡀⠀⠀⠀⠀
⠀⠀⠀⠀⢀⡴⠃⢀⡴⢳⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠙⣆⠀⠀⠀
⠀⠀⠀⠀⡾⠁⣠⠋⠀⠈⢧⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠈⢧⠀⠀
⠀⠀⠀⣸⠁⢰⠃⠀⠀⠀⠈⢣⡀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠈⣇⠀
⠀⠀⠀⡇⠀⡾⡀⠀⠀⠀⠀⣀⣹⣆⡀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢹⠀
⠀⠀⢸⠃⢀⣇⡈⠀⠀⠀⠀⠀⠀⢀⡑⢄⡀⢀⡀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢸⡇
⠀⠀⢸⠀⢻⡟⡻⢶⡆⠀⠀⠀⠀⡼⠟⡳⢿⣦⡑⢄⠀⠀⠀⠀⠀⠀⠀⠀⢸⡇
⠀⠀⣸⠀⢸⠃⡇⢀⠇⠀⠀⠀⠀⠀⡼⠀⠀⠈⣿⡗⠂⠀⠀⠀⠀⠀⠀⠀⢸⠁
⠀⠀⡏⠀⣼⠀⢳⠊⠀⠀⠀⠀⠀⠀⠱⣀⣀⠔⣸⠁⠀⠀⠀⠀⠀⠀⠀⢠⡟⠀
⠀⠀⡇⢀⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠠⠀⡇⠀⠀⠀⠀⠀⠀⠀⠀⢸⠃⠀
⠀⢸⠃⠘⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢸⠁⠀⠀⢀⠀⠀⠀⠀⠀⣾⠀⠀
⠀⣸⠀⠀⠹⡄⠀⠀⠈⠁⠀⠀⠀⠀⠀⠀⠀⡞⠀⠀⠀⠸⠀⠀⠀⠀⠀⡇⠀⠀
⠀⡏⠀⠀⠀⠙⣆⠀⠀⠀⠀⠀⠀⠀⢀⣠⢶⡇⠀⠀⢰⡀⠀⠀⠀⠀⠀⡇⠀⠀
⢰⠇⡄⠀⠀⠀⡿⢣⣀⣀⣀⡤⠴⡞⠉⠀⢸⠀⠀⠀⣿⡇⠀⠀⠀⠀⠀⣧⠀⠀
⣸⠀⡇⠀⠀⠀⠀⠀⠀⠉⠀⠀⠀⢹⠀⠀⢸⠀⠀⢀⣿⠇⠀⠀⠀⠁⠀⢸⠀⠀
⣿⠀⡇⠀⠀⠀⠀⠀⢀⡤⠤⠶⠶⠾⠤⠄⢸⠀⡀⠸⣿⣀⠀⠀⠀⠀⠀⠈⣇⠀
⡇⠀⡇⠀⠀⡀⠀⡴⠋⠀⠀⠀⠀⠀⠀⠀⠸⡌⣵⡀⢳⡇⠀⠀⠀⠀⠀⠀⢹⡀
⡇⠀⠇⠀⠀⡇⡸⠁⠀⠀⠀⠀⠀⠀⠀⠀⠀⠙⠮⢧⣀⣻⢂⠀⠀⠀⠀⠀⠀⢧
⣇⠀⢠⠀⠀⢳⠇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠈⡎⣆⠀⠀⠀⠀⠀⠘
⢻⠀⠈⠰⠀⢸⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠰⠘⢮⣧⡀⠀⠀⠀⠀
⠸⡆⠀⠀⠇⣾⠀⠀⠀⠀⠀⠀⠀⠀⠀⢠⠆⠀⠀⠀⠀⠀⠀⠀⠙⠳⣄⡀⢢⡀
<3 <3 <3 <3 <3 <3 <3 <3 <3 <3 <3 <3 <3
*/
