#include <bits/stdc++.h>
#define int long long
#define IO ios::sync_with_stdio(0), cin.tie(0)
#define FOR(i, a, b) for (int i = a, I = b; i <= I; i++)
using namespace std;
using pii = pair<int, int>;
void dbg() {;}
template<class T, class ...U>
void dbg(T a, U ...b) { cout << a << " "; dbg(b...); }
void ent() { cout << "\n"; }
const int INF = 1e17;
const int N = 205;
int a[N], t[N];
int dp[2][N][N][N];
signed main() {
IO;
int n, len;
cin >> n >> len;
FOR(i, 1, n) cin >> a[i];
FOR(i, 1, n) cin >> t[i];
int ans = 0;
fill(&dp[0][0][0][0], &dp[0][0][0][0] + 2 * N * N * N, INF);
dp[0][0][0][n] = 0;
for (int i = 0; i < n; i++) {
for (int r = n; r >= 1; r--) {
// Left : 0
for (int l = 0; l <= r; l++) {
if (dp[0][i][l][r] < INF) {
int ti, nxt_i;
ti = dp[0][i][l][r] + (a[l + 1] - a[l]);
nxt_i = i + (ti <= t[l + 1]);
dp[0][nxt_i][l + 1][r] = min(dp[0][nxt_i][l + 1][r], ti);
ti = dp[0][i][l][r] + (a[l] - 0 + len - a[r]);
nxt_i = i + (ti <= t[r]);
dp[1][nxt_i][l + 1][r] = min(dp[1][nxt_i][l + 1][r], ti);
}
}
// Right : 1
for (int l = 0; l <= r; l++) {
if (dp[1][i][l][r] < INF) {
int ti, nxt_i;
ti = dp[1][i][l][r] + (len - a[r] + a[l] - 0);
nxt_i = i + (ti <= t[l]);
dp[0][nxt_i][l][r - 1] = min(dp[0][nxt_i][l][r - 1], ti);
ti = dp[1][i][l][r] + (a[r] - a[r - 1]);
nxt_i = i + (ti <= t[r - 1]);
dp[1][nxt_i][l][r - 1] = min(dp[1][nxt_i][l][r - 1], ti);
}
}
}
}
for (int i = 1; i <= n; i++)
for (int l = 1; l <= n; l++)
for (int r = l; r <= n; r++)
if (dp[0][i][l][r] < INF || dp[1][i][l][r] < INF)
ans = max(ans, i);
cout << ans << "\n";
return 0;
}
