#include <iostream>
#include <bits/stdc++.h>
#define ll long long
using namespace std;
const ll maxn = 205, INF = 4e18+9;
struct stamp{
ll x, t;
};
ll dp[maxn][maxn][maxn][2];
void solve(){
int n, L;
cin >> n >> L;
vector<stamp> a(n+2);
for(int i = 1; i <= n; i++){
cin >> a[i].x;
}
for(int i = 1; i <= n; i++){
cin >> a[i].t;
}
a[0] = {0, INF};
a[n+1] = {0, INF};
auto C = [&](int i, int j) -> ll{
if(a[i].x < a[j].x) swap(i, j);
return min(a[i].x - a[j].x, L+(a[j].x-a[i].x));
};
auto chmin = [&](ll &a, ll b) -> void{
a = min(a, b);
};
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[1][n][0][0] = dp[1][n][0][1] = 0;
for(int len = n-1; len >= 0; len--){
for(int i = 1; i <= n-len+1; i++){
int j = i+len-1;
for(int k = 0; k <= n; k++){
if(i > 1) chmin(dp[i][j][k][0], dp[i-1][j][k][0] + C(i-1, i-1-1));
if(j < n) chmin(dp[i][j][k][1], dp[i][j+1][k][1] + C(j+1, j+1+1));
if(i > 1) chmin(dp[i][j][k][0], dp[i-1][j][k][1] + C(j+1, i-1));
if(j < n) chmin(dp[i][j][k][1], dp[i][j+1][k][0] + C(i-1, j+1));
if(k == 0) continue;
if(i > 1 && dp[i-1][j][k-1][0] + C(i-1, i-1-1) <= a[i-1].t) chmin(dp[i][j][k][0], dp[i-1][j][k-1][0] + C(i-1, i-1-1));
if(j < n && dp[i][j+1][k-1][1] + C(j+1, j+1+1) <= a[j+1].t) chmin(dp[i][j][k][1], dp[i][j+1][k-1][1] + C(j+1, j+1+1));
if(i > 1 && dp[i-1][j][k-1][1] + C(j+1, i-1) <= a[i-1].t) chmin(dp[i][j][k][0], dp[i-1][j][k-1][1] + C(j+1, i-1));
if(j < n && dp[i][j+1][k-1][0] + C(i-1, j+1) <= a[j+1].t) chmin(dp[i][j][k][1], dp[i][j+1][k-1][0] + C(i-1, j+1));
}
}
}
int ans = 0;
for(int i = 0; i <= n; i++){
for(int j = 0; j <= n; j++){
for(int k = n; k >= 0; k--){
if(min(dp[i][j][k][0], dp[i][j][k][1]) < INF){
ans = max(ans, k);
}
}
}
}
cout << ans;
}
int main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL);
solve();
}
