/**
____ ____ ____ ____ ____
||a |||t |||o |||d |||o ||
||__|||__|||__|||__|||__||
|/__\|/__\|/__\|/__\|/__\|
**/
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N_MAX = 200;
const int INF = INT_MAX / 2;
const int LEFT = 0;
const int RIGHT = 1;
int N, L;
int X[N_MAX + 2];
int T[N_MAX + 2];
int minT[N_MAX + 2][N_MAX + 2][N_MAX + 2][2];
// minT[k][l][r][last] = Minimum time required to get k stamps,
// visiting the first l stands and the last r stands,
// the final position being at l or at r depending on last
void update (int &x, const int &y) {
if (y < x) {
x = y;
}
}
int main () {
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
cin >> N >> L;
for (int i = 1; i <= N; i++) {
cin >> X[i];
}
for (int i = 1; i <= N; i++) {
cin >> T[i];
}
X[0] = 0;
X[N + 1] = L;
for (int k = 0; k <= N; k++) {
for (int l = 0; l <= N; l++) {
for (int r = 0; r <= N; r++) {
minT[k][l][r][LEFT] = INF;
minT[k][l][r][RIGHT] = INF;
}
}
}
minT[0][0][0][LEFT] = 0;
minT[0][0][0][RIGHT] = 0;
for (int k = 0; k <= N; k++) {
for (int l = 0; l <= N; l++) {
for (int r = 0; l + r < N; r++) {
int swpSide = X[l] + (L - X[(N + 1) - r]);
update(minT[k][l][r][LEFT], minT[k][l][r][RIGHT] + swpSide);
update(minT[k][l][r][RIGHT], minT[k][l][r][LEFT] + swpSide);
int newTLeft = minT[k][l][r][LEFT] + (X[l + 1] - X[l]);
int newTRight = minT[k][l][r][RIGHT] + (X[(N + 1) - r] - X[(N + 1) - (r + 1)]);
update(minT[k + (newTLeft <= T[l + 1])][l + 1][r][LEFT], newTLeft);
update(minT[k + (newTRight <= T[(N + 1) - (r + 1)])][l][r + 1][RIGHT], newTRight);
}
}
}
int answer = 0;
for (int k = 0; k <= N; k++) {
for (int l = 0; l <= N; l++) {
for (int r = (l == 0); l + r <= N; r++) {
if (minT[k][l][r][LEFT] != INF || minT[k][l][r][RIGHT] != INF) {
answer = k;
}
}
}
}
cout << answer << "\n";
return 0;
}
