#include <bits/stdc++.h>
#define fi first
#define se second
#define mp make_pair
#define Sz(x) (int)x.size()
using namespace std;
const int N = 205;
const int inf = INT_MAX;
int n, l, x[N], t[N], dp[2][N][N][N];
int dist(int a, int b) {
if (a > b) swap(a, b);
return min(b - a, l - b + a);
}
void solve() {
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 - i; j++) {
for (int k = 0; k <= n; k++) {
dp[0][i][j][k] = dp[1][i][j][k] = inf;
}
}
}
dp[0][0][0][0] = dp[1][0][0][0] = 0;
for (int k = 0; k <= n; k++) {
for (int tp = 0; tp < 2; tp++) {
for (int i = 0; i <= n; i++) {
for (int j = 0; j <= n - i; j++) {
if (dp[tp][i][j][k] == inf) continue;
int time = dp[tp][i][j][k], pos, k2 = k;
int time2 = time;
if (tp == 0) {
if (i == 0) pos = 0;
else pos = x[i];
}
else {
if (j == 0) pos = 0;
else pos = x[n - j + 1];
}
int pos2 = pos;
for (int i2 = i + 1; i2 + j <= n; i2++) {
time += dist(pos, x[i2]);
pos = x[i2];
if (time <= t[i2]) k2++;
dp[0][i2][j][k2] = min(dp[0][i2][j][k2], time);
}
pos = pos2, k2 = k, time = time2;
for (int j2 = j + 1; j2 + i <= n; j2++) {
time += dist(pos, x[n - j2 + 1]);
pos = x[n - j2 + 1];
if (time <= t[n - j2 + 1]) k2++;
dp[1][i][j2][k2] = min(dp[1][i][j2][k2], time);
}
}
}
}
}
int ans = 0;
for (int tp = 0; tp < 2; tp++) {
for (int i = 0; i <= n; i++) {
for (int j = 0; j <= n - i; j++) {
for (int k = 0; k <= n; k++) {
if (dp[tp][i][j][k] != inf) ans = max(ans, k);
}
}
}
}
cout << ans;
}
signed main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
int tt = 1;
// cin >> tt;
while (tt--) {
solve();
// cout << '\n';
}
}
