#include <bits/stdc++.h>
#define pb push_back
#define ll long long int
#define all(v) (v).begin(),(v).end()
#define fi first
#define se second
using namespace std;
ll n, l; int mx = 0;
ll dp[205][205][2][205] = { };
int main() {
cin >> n >> l; vector<ll> x(n+5), t(n+5);
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 < 205; i++) {
for (int j = 0; j < 205; j++) {
for (int k = 0; k < 205; k++) {
dp[i][j][0][k] = 1e18;
dp[i][j][1][k] = 1e18;
}
}
}
x[n+1] = l;
dp[n+1][0][0][0] = 0;
dp[n+1][0][1][0] = 0;
if (1) {
// dp[n+1][?][1][?]
int cur = 0;
for (int i = 1; i <= n; i++) {
if (x[i] <= t[i]) cur++;
dp[n+1][i][1][cur] = min(dp[n+1][i][1][cur], x[i]);
}
// dp[?][0][0][?]
cur = 0;
for (int i = n; i > 0; i--) {
if (l-x[i] <= t[i]) cur++;
dp[i][0][0][cur] = min(dp[i][0][0][cur], l-x[i]);
}
}
for (int i = n; i > 0; i--) {
for (int j = 1; j < i; j++) {
for (int k = 1; k <= n; k++) {
// dp[i][j][0][?]: i+1 -> i
ll cur = dp[i+1][j][0][k] + x[i+1] - x[i];
dp[i][j][0][k] = min(dp[i][j][0][k], cur);
cur = dp[i+1][j][0][k-1] + x[i+1] - x[i];
if (cur <= t[i]) {
dp[i][j][0][k] = min(dp[i][j][0][k], cur);
}
// dp[i][j][0][?]: j -> i
cur = dp[i+1][j][1][k] + x[i] - x[j];
dp[i][j][0][k] = min(dp[i][j][0][k], cur);
cur = dp[i+1][j][1][k-1] + x[i] - x[j];
if (cur <= t[i]) {
dp[i][j][0][k] = min(dp[i][j][0][k], cur);
}
// dp[i][j][1][?]: j-1 -> j
cur = dp[i][j-1][1][k] + x[j] - x[j-1];
dp[i][j][1][k] = min(dp[i][j][1][k], cur);
cur = dp[i][j-1][1][k-1] + x[j] - x[j-1];
if (cur <= t[j]) {
dp[i][j][1][k] = min(dp[i][j][1][k], cur);
}
// dp[i][j][1][?]: i -> j
cur = dp[i][j-1][0][k] + l - x[i] + x[j];
dp[i][j][1][k] = min(dp[i][j][1][k], cur);
cur = dp[i][j-1][0][k-1] + l - x[i] + x[j];
if (cur <= t[j]) {
dp[i][j][1][k] = min(dp[i][j][1][k], cur);
}
}
}
}
for (int i = 0; i <= n+1; i++) {
for (int j = 0; j <= n+1; j++) {
for (int k = 0; k <= n; k++) {
if (dp[i][j][0][k] < 1e18) mx = max(mx, k);
if (dp[i][j][1][k] < 1e18) mx = max(mx, k);
}
}
}
cout << mx;
return 0;
}
