// In the name of God
#include<bits/stdc++.h>
using namespace std;
#define pb push_back
#define fi first
#define se second
#define mp make_pair
typedef long long ll;
const int N = 200 + 5;
int n, L, X[N], T[N];
ll dp[N][N][N][2];
void solve() {
cin >> n >> L;
for (int i = 1; i <= n; i++)
cin >> X[i];
for (int i = 1; i <= n; i++)
cin >> T[i];
memset(dp, 63, sizeof dp);
X[n + 1] = L;
dp[0][n + 1][0][0] = dp[0][n + 1][0][1] = 0;
int ans = 0;
for (int i = 0; i <= n; i++) {
for (int j = n + 1; j > i; j--) {
for (int k = 0; k <= n; k++) {
if (i == 0 && j == n + 1 && k == 0)
continue;
ll x = 1e17;
if (i) {
x = dp[i - 1][j][k][0] + X[i] - X[i - 1];
if (dp[i - 1][j][k - 1][0] + X[i] - X[i - 1] <= T[i]) {
x = min(x, dp[i - 1][j][k - 1][0] + X[i] - X[i - 1]);
}
x = min(x, dp[i - 1][j][k][1] + X[i] + L - X[j]);
if (dp[i - 1][j][k - 1][1] + X[i] + L - X[j] <= T[i]) {
x = min(x, dp[i - 1][j][k - 1][1] + X[i] + L - X[j]);
}
}
if (x < 1e17)
ans = max(ans, k);
dp[i][j][k][0] = x;
x = 1e17;
if (j < n + 1) {
x = dp[i][j + 1][k][1] + X[j + 1] - X[j];
if (dp[i][j + 1][k - 1][1] + X[j + 1] - X[j] <= T[j])
x = min(x, dp[i][j + 1][k - 1][1] + X[j + 1] - X[j]);
x = min(x, dp[i][j + 1][k][0] + X[i] + L - X[j]);
if (dp[i][j + 1][k - 1][0] + X[i] + L - X[j] <= T[j])
x = min(x, dp[i][j + 1][k - 1][0] + X[i] + L - X[j]);
}
if (x < 1e17)
ans = max(ans, k);
dp[i][j][k][1] = x;
}
}
}
cout << ans << endl;
}
int32_t main() {
ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
int tc = 1; // cin >> tc;
while (tc--) {
solve();
}
return 0;
}
