#include <bits/stdc++.h>
using namespace std;
#define int long long
const int N = 202;
int n, l;
int x[N], t[N];
int dp[N][N][N][2];
bool seen[N][N][N][2];
int calc(int i, int j, int k, int s) {
if (seen[i][j][k][s])
return dp[i][j][k][s];
seen[i][j][k][s] = true;
int &val = dp[i][j][k][s];
if (i + j < k || (i == 0 && s == 0) || (j == 0 && s == 1) || i + j > n)
return val = 1e11;
if (k == 0) {
if (s == 0)
return val = x[i];
else
return val = l - x[n - j + 1];
}
if (j == 0) {
int temp = calc(i - 1, j, k - 1, s);
if (temp + x[i] - x[i - 1] <= t[i])
val = min(val, temp + x[i] - x[i - 1]);
return val = min(val, calc(i - 1, j, k, s) + x[i] - x[i - 1]);
}
if (i == 0) {
int temp = calc(i, j - 1, k - 1, s);
if (temp + abs(x[n - j + 2] - x[n - j + 1]) <= t[n - j + 1])
val = min(val, temp + abs(x[n - j + 2] - x[n - j + 1]));
return val = min(val, calc(i, j - 1, k, s) + abs(x[n - j + 2] - x[n - j + 1]));
}
if (s == 0) {
int temp = calc(i - 1, j, k - 1, s);
if (temp + x[i] - x[i - 1] <= t[i])
val = min(val, temp + x[i] - x[i - 1]);
val = min(val, calc(i - 1, j, k, s) + x[i] - x[i - 1]);
temp = calc(i - 1, j, k - 1, 1);
if (temp + x[i] + l - x[n - j + 1] <= t[i])
val = min(val, temp + x[i] + l - x[n - j + 1]);
return val = min(val, calc(i - 1, j, k, 1) + x[i] + l - x[n - j + 1]);
}
if (s == 1) {
int temp = calc(i, j - 1, k - 1, s);
if (temp + abs(x[n - j + 2] - x[n - j + 1]) <= t[n - j + 1])
val = min(val, temp + abs(x[n - j + 2] - x[n - j + 1]));
val = min(val, calc(i, j - 1, k, s) + abs(x[n - j + 2] - x[n - j + 1]));
temp = calc(i, j - 1, k - 1, 0);
if (temp + x[i] + l - x[n - j + 1] <= t[n - j + 1])
val = min(val, temp + x[i] + l - x[n - j + 1]);
return val = min(val, calc(i, j - 1, k, 0) + x[i] + l - x[n - j + 1]);
}
}
void solveTestCase() {
cin >> n >> l;
for (int i = 1; i <= n; i++) cin >> x[i];
for (int i = 1; i <= n; i++) cin >> t[i];
x[n + 1] = l;
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] = 1e11;
}
}
dp[0][0][0][0] = dp[0][0][0][1] = 0;
seen[0][0][0][0] = seen[0][0][0][1] = true;
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] = calc(i, j, k, 0), dp[i][j][k][1] = calc(i, j, k, 1);
}
}
int ans = 0;
for (int i = 0; i <= n; i++) {
for (int j = 0; j <= n; j++) {
for (int k = 0; k <= n; k++) {
int a1 = dp[i][j][k][0], a2 = dp[i][j][k][1];
if (dp[i][j][k][0] < 1e11)
ans = max(ans, k);
if (dp[i][j][k][1] < 1e11)
ans = max(ans, k);
}
}
}
cout << ans;
}
signed main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
int test = 1;
//cin >> test;
while (test--)
solveTestCase();
}
