/*DavitMarg*/
#include <iostream>
#include <algorithm>
#include <cmath>
#include <vector>
#include <string>
#include <cstring>
#include <map>
#include <unordered_map>
#include <set>
#include <queue>
#include <iomanip>
#include <bitset>
#include <stack>
#include <cassert>
#include <iterator>
#include <fstream>
#define mod 1000000007ll
#define LL long long
#define LD long double
#define MP make_pair
#define PB push_back
#define all(v) v.begin(), v.end()
using namespace std;
const int N = 205;
int n, L, x[N], t[N], ans;
int dp[N][N][N][2];
int sf(int x)
{
return n - x + 1;
}
int main()
{
cin >> n >> L;
for (int i = 1; i <= n; i++)
cin >> x[i];
for (int i = 1; i <= n; i++)
cin >> t[i];
for (int s = 0; s <= n; s++)
for (int p = 0; p <= n; p++)
for (int i = 0; i <= n; i++)
dp[p][s][i][0] = dp[p][s][i][1] = mod;
dp[0][0][0][1] = dp[0][0][0][0] = 0;
x[n + 1] = L;
for (int c = 0; c < n; c++)
for (int p = 0; p <= c; p++)
for (int C = 0; C < n; C++)
{
int s = c - p;
int T;
//left
T = dp[p][s][C][0];
dp[p + 1][s][C + (T + x[p + 1] - x[p] <= t[p + 1])][0] = min(dp[p + 1][s][C + (T + x[p + 1] - x[p] <= t[p + 1])][0],T + x[p + 1] - x[p]);
dp[p][s + 1][C + (T + x[p] + L - x[sf(s + 1)] <= t[sf(s + 1)])][1] = min(dp[p][s + 1][C + (T + x[p] + L - x[sf(s + 1)] <= t[sf(s + 1)])][1],T + x[p] + L - x[sf(s + 1)]);
//right
T = dp[p][s][C][1];
dp[p][s + 1][C + (T + x[sf(s)] - x[sf(s + 1)] <= t[sf(s + 1)])][1] = min(dp[p][s + 1][C + (T + x[sf(s)] - x[sf(s + 1)] <= t[sf(s + 1)])][1], T + x[sf(s)] - x[sf(s + 1)]);
dp[p + 1][s][C + (T + x[p + 1] + L - x[sf(s)] <= t[p + 1])][0] = min(dp[p + 1][s][C + (T + x[p + 1] + L - x[sf(s)] <= t[p + 1])][0], T + x[p + 1] + L - x[sf(s)]);
}
for (int c = 0; c <= n; c++)
for (int p = 0; p <= n; p++)
for (int s = 0; s <= n; s++)
for (int d = 0; d <= 1; d++)
if (dp[p][s][c][d] != mod)
ans = c;
cout << ans << endl;
return 0;
}
/*
5
1 2 3 4 5
5 4 3 2 1
*/
