#include <bits/stdc++.h>
#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
using namespace std;
#define threesum cin.tie(NULL); cout.tie(NULL); ios_base::sync_with_stdio(false)
#define all(a) a.begin(), a.end()
#define F first
#define S second
#define int long long
#define pii pair<int, int>
#define ppp pair<int, pii>
#define dout cout << fixed << setprecision(15)
#define mid ((l + r) >> 1)
#define lc (id << 1)
#define rc (lc + 1)
const int maxn = 2e5 + 10, maxm = 2e2 + 10, oo = 1e18, lg = 19, sq = 1400, mod = 998244353;
int n, ln, ans;
int x[maxm], t[maxm];
int dp[2][maxm][maxm][maxm];
int d(int x, int y){
return min(abs(x - y), ln - (abs(x - y)));
}
void solve()
{
cin >> n >> ln;
for (int i = 1; i <= n; i++)
cin >> x[i];
for (int i = 1; i <= n;i++)
cin >> t[i];
x[0] = 0;
x[n + 1] = ln;
t[0] = -oo;
t[n + 1] = -oo;
for (int b = 0; b < 2;b++)
for (int l = 0; l <= n + 5; l++)
for (int r = 0; r <= n + 5; r++)
for (int k = 0; k <= n + 5;k++)
dp[b][l][r][k] = oo;
dp[0][0][n + 1][0] = 0;
dp[1][0][n + 1][0] = 0;
for (int l = 0; l < n; l++)
for (int r = n + 1; r - 1 > l; r--)
for (int k = 0; k <= n; k++){
int tm;
tm = min(dp[0][l][r][k] + d(x[l + 1], x[l]), dp[1][l][r][k] + d(x[l + 1], x[r]));
if(tm <= t[l + 1])
dp[0][l + 1][r][k + 1] = min(dp[0][l + 1][r][k + 1], tm);
else
dp[0][l + 1][r][k] = min(dp[0][l + 1][r][k], tm);
tm = min(dp[0][l][r][k] + d(x[r - 1], x[l]), dp[1][l][r][k] + d(x[r - 1], x[r]));
if(tm <= t[r - 1])
dp[1][l][r - 1][k + 1] = min(dp[1][l][r - 1][k + 1], tm);
else
dp[1][l][r - 1][k] = min(dp[1][l][r - 1][k], tm);
}
for (int b = 0; b < 2;b++)
for (int l = 0; l <= n + 5; l++)
for (int r = 0; r <= n + 5; r++)
for (int k = 0; k <= n + 5;k++)
if(dp[b][l][r][k] < oo)
ans = max(ans, k);
cout << ans;
}
signed main()
{
threesum;
int t = 1;
//cin >> t;
while(t--)
solve();
}
/*
10 87
9 23 33 38 42 44 45 62 67 78
15 91 7 27 31 53 12 91 89 46
*/
