#include<bits/stdc++.h>
#define taskname "C"
using namespace std;
typedef long long ll;
const ll INF = 1e18;
template<class T>void minimize(T& a, T b){
if(a > b){
a = b;
}
}
template<class T>void maximize(T& a, T b){
if(a < b){
a = b;
}
}
const int lim = 205;
int n, L, x[lim], t[lim];
namespace sub1{
void solve(){
vector<vector<bool>>dp(L + 1, vector<bool>(1 << n, false));
dp[1][0] = true;
auto fix = [&] (int time){
for(int i = 1; i <= L; i++){
for(int mask = (1 << n) - 1; mask > -1; mask--){
if(dp[i][mask]){
for(int j = 1; j <= n; j++){
if(x[j] == i && t[j] >= time){
dp[i][mask | (1 << (j - 1))] = true;
break;
}
}
}
}
}
};
fix(1);
for(int time = 2; time < lim; time++){
vector<vector<bool>>ndp(L + 1, vector<bool>(1 << n, false));
for(int i = 1; i <= L; i++){
for(int mask = (1 << n) - 1; mask > -1; mask--){
if(dp[i][mask]){
ndp[i == 1 ? L - 1 : i - 1][mask] = ndp[i == L - 1 ? 1 : i + 1][mask] = true;
}
}
}
swap(dp, ndp);
fix(time);
}
int ans = 0;
for(int i = 1; i <= L; i++){
for(int mask = (1 << n) - 1; mask > 0; mask--){
if(dp[i][mask]){
maximize(ans, __builtin_popcount(mask));
}
}
}
cout << ans;
}
}
namespace sub234{
ll f[lim][lim][2][lim];
ll dp(int l, int r, bool dir, int k){
if(k == 0){
return INF;
}
if(l > r){
return -INF;
}
ll& ans = f[l][r][dir][k];
if(ans != -1){
return ans;
}
int current = (dir ? x[r + 1] : x[l - 1]), ld = abs(current - x[l]), rd = abs(current - x[r]);
minimize(ld, L - ld);
minimize(rd, L - rd);
return ans = max({dp(l + 1, r, false, k) - ld, dp(l, r - 1, true, k) - rd, min(ll(t[l]), dp(l + 1, r, false, k - 1)) - ld, min(ll(t[r]), dp(l, r - 1, true, k - 1)) - rd});
}
void solve(){
memset(f, -1, sizeof(f));
x[n + 1] = 0;
for(int i = n; i > 0; i--){
if(dp(1, n, true, i) > -1){
return void(cout << i);
}
}
cout << 0;
}
}
int main(){
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
if(fopen(taskname".inp", "r")){
freopen(taskname".inp", "r", stdin);
}
cin >> n >> L;
for(int i = 1; i <= n; i++){
cin >> x[i];
}
for(int i = 1; i <= n; i++){
cin >> t[i];
}
if(n <= 12 && L <= 200 && *max_element(t + 1, t + n + 1) <= 200){
sub1::solve();
}
else{
sub234::solve();
}
}
