#include <bits/stdc++.h>
using namespace std;
const int N = 203;
const long long oo = 1e18;
void mini(long long &X, long long Y) {
if (X > Y) X = Y;
}
int n, l, x[N], ti[N];
long long dp[N][N][N][2];
void solve(void) {
cin >> n >> l;
x[0] = 0; x[n + 1] = l;
for (int i = 1; i <= n; i++) cin >> x[i];
for (int i = 1; i <= n; i++) cin >> ti[i];
for (int p = 0; p <= n; p++) {
for (int s = p + 1; s <= n + 1; s++) {
for (int score = 0; score <= n; score++) {
dp[p][s][score][0] = dp[p][s][score][1] = oo;
}
}
}
dp[0][n + 1][0][0] = dp[0][n + 1][0][1] = 0;
for (int p = 0; p <= n; p++) {
for (int s = n + 1; s > p; s--) {
for (int score = 0; score <= n; score++) {
int t;
if (dp[p][s][score][1] < oo) {
t = 0;
for (int i = p + 1; i < s; i++) {
t += 2 * dp[p][s][score][1] + x[i] <= ti[i];
mini(dp[i][s][score + t][0], dp[p][s][score][1] + x[i]);
}
}
if (dp[p][s][score][0] < oo) {
t = 0;
for (int i = s - 1; i > p; i--) {
t += 2 * dp[p][s][score][0] + l - x[i] <= ti[i];
mini(dp[p][i][score + t][1], dp[p][s][score][0] + l - x[i]);
}
}
}
}
}
int ans = 0;
for (int i = 1; i <= n + 1; i++) {
for (int score = n; score; score--) {
if (min(dp[i - 1][i][score][0], dp[i - 1][i][score][1]) < oo) {
ans = max(ans, score);
break;
}
}
}
cout << ans;
}
signed main(void) {
ios::sync_with_stdio(false); cin.tie(nullptr);
int T = 1;// cin >> T;
while (T--) solve();
return 0;
}
