#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
#include "debug.h"
#else
#define debug(...) 42
#endif
const int N = 205, inf = 1e9 + 7;
int n, l;
int x[N], t[N], dp[N][N][N][2];
int main() {
ios::sync_with_stdio(false); cin.tie(nullptr);
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 i = 0; i <= n; ++i) {
for (int j = 0; j <= n + 1; ++j) {
for (int k = 0; k <= n; ++k) {
for (int x = 0; x < 2; ++x) {
dp[i][j][k][x] = inf;
}
}
}
}
dp[0][n + 1][0][0] = 0;
for (int i = 0; i < n; ++i) {
for (int j = n + 1; j > i + 1; --j) {
for (int cnt = 0; cnt <= n; ++cnt) {
if (dp[i][j][cnt][0] != inf) {
int c = dp[i][j][cnt][0] + x[i + 1] - x[i];
int ncnt = cnt + (c <= t[i + 1]);
dp[i + 1][j][ncnt][0] = min(dp[i + 1][j][ncnt][0], c);
c = dp[i][j][cnt][0] + x[i] + l - x[j - 1];
ncnt = cnt + (c <= t[j - 1]);
dp[i][j - 1][ncnt][1] = min(dp[i][j - 1][ncnt][1], c);
}
if (dp[i][j][cnt][1] != inf) {
int c = dp[i][j][cnt][1] + l - x[j] + x[i + 1];
int ncnt = cnt + (c <= t[i + 1]);
dp[i + 1][j][ncnt][0] = min(dp[i + 1][j][ncnt][0], c);
c = dp[i][j][cnt][1] + x[j] - x[j - 1];
ncnt = cnt + (c <= t[j - 1]);
dp[i][j - 1][ncnt][1] = min(dp[i][j - 1][ncnt][1], c);
}
}
}
}
int res = 0;
for (int i = 0; i <= n; ++i) {
for (int j = 0; j <= n + 1; ++j) {
for (int k = 0; k <= n; ++k) {
for (int x = 0; x < 2; ++x) {
if (dp[i][j][k][x] < inf) {
res = max(res, k);
}
}
}
}
}
cout << res;
return 0;
}
