#include <bits/stdc++.h>
using namespace std;
const int MN = 201;
const int INF = 1e9 + 1;
using ll = long long;
int n, l, P[MN], T[MN];
ll DP[MN][MN][MN][2];
int dist(int p1, int p2) {
return min(abs(p2 - p1), l - abs(p2 - p1));
}
int main() {
cin >> n >> l;
for(int i = 1; i <= n; ++i)
cin >> P[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) {
for(int w = 0; w < 2; ++w) {
DP[i][j][k][w] = INF;
}
}
}
}
DP[0][0][0][0] = 0;
int re = 0;
for(int i = 0; i <= n; ++i) {
for(int j = 0; j <= n; ++j) {
for(int k = 0; k <= n; ++k) {
for(int w = 0; w < 2; ++w) {
if(DP[i][j][k][w] < INF) {
re = max(re, k);
if(i + j == n) continue; /// am vizitat tot
int poz = w ? P[j] : P[n - i + 1];
///dreapta
int d = dist(poz, P[j + 1]), win = (T[j + 1] >= (d + DP[i][j][k][w]));
DP[i][j + 1][k + win][1] = min(DP[i][j + 1][k + win][1], d + DP[i][j][k][w]);
///stanga
d = dist(poz, P[n - i]);
win = T[n - i] >= (d + DP[i][j][k][w]);
DP[i + 1][j][k + win][0] = min(DP[i + 1][j][k + win][0], d + DP[i][j][k][w]);
}
}
}
}
}
cout << re << "\n";
return 0;
}
