#include <bits/stdc++.h>
#define ll long long
using namespace std;
const ll INF = 1e18;
ll dp[207][207][207][2];
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
ll n,l;
cin >> n >> l;
vector<ll> x(n+1),t(n+1);
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; j++) {
for (int k=0; k<=n; k++) dp[i][j][k][0] = dp[i][j][k][1] = INF;
}
}
dp[0][0][0][0] = dp[0][0][0][1] = 0;
for (int s=0; s<n; s++) {
for (int i=0; i<=s; i++) {
ll j = s-i;
for (int k=0; k<=s; k++) {
if (dp[i][j][k][0]!=INF) {
ll t1 = dp[i][j][k][0]+(x[i+1]-x[i]);
ll k1 = k+(t1<=t[i+1] ? 1 : 0);
dp[i+1][j][k1][0] = min(dp[i+1][j][k1][0], t1);
t1 = dp[i][j][k][0]+(x[i]+(l-x[n-j]));
k1 = k+(t1<=t[n-j] ? 1 : 0);
dp[i][j+1][k1][1] = min(dp[i][j+1][k1][1], t1);
}
if (dp[i][j][k][1]!=INF) {
ll curr = (j==0 ? 0 : x[n-j+1]);
ll t1 = dp[i][j][k][1]+((j==0 ? x[i+1] : (l-curr+x[i+1])));
ll k1 = k+(t1<=t[i+1] ? 1 : 0);
dp[i+1][j][k1][0] = min(dp[i+1][j][k1][0], t1);
t1 = dp[i][j][k][1]+((j==0 ? l-x[n] : curr-x[n-j]));
k1 = k+(t1<=t[n-j] ? 1 : 0);
dp[i][j+1][k1][1] = min(dp[i][j+1][k1][1], t1);
}
}
}
}
ll res = 0;
for (int i=0; i<=n; i++) {
for (int j=0; i+j<=n; j++) {
for (ll k=0; k<=n; k++) {
if (dp[i][j][k][0]!=INF || dp[i][j][k][1]!=INF) {
res = max(res, k);
}
}
}
}
cout << res;
}
