#include <bits/stdc++.h>
using namespace std;
#define task "main"
#define no "NO"
#define yes "YES"
#define F first
#define S second
#define vec vector
#define _mp make_pair
#define ii pair<int, int>
#define li pair<long long, int>
#define sz(x) (int)x.size()
#define all(x) x.begin(), x.end()
#define evoid(val) return void(std::cout << val)
#define FOR(i, a, b) for(int i = (a); i <= (b); ++i)
#define FOD(i, b, a) for(int i = (b); i >= (a); --i)
const int MAX_N = (int)2e2 + 4;
const long long INF = (long long)1e18 + 1408;
int n, l;
long long pos[MAX_N];
int timeLimit[MAX_N];
namespace sub2 {
li dp[1 << 15][20];
long long dist(long long x, long long y) {
if (x > y) swap(x, y);
return min(y - x, x + l - y);
}
void solve() {
FOR(mask, 1, (1 << n) - 1) {
FOR(i, 0, n - 1) {
dp[mask][i] = {INF, 0};
if (!((mask >> i) & 1)) continue;
if (__builtin_popcount(mask) == 1) {
dp[mask][i].F = dist(0, pos[i + 1]);
if (dp[mask][i].F <= timeLimit[i + 1]) dp[mask][i].S = 1;
continue;
}
int preMask = (mask ^ (1 << i));
FOR(last, 0, n - 1) {
if (!((preMask >> last) & 1)) continue;
long long tmp = dp[preMask][last].F + dist(pos[last + 1], pos[i + 1]);
if (tmp <= timeLimit[i + 1]) {
if (dp[preMask][last].S + 1 > dp[mask][i].S)
dp[mask][i] = {tmp, dp[preMask][last].S + 1};
else if (dp[preMask][last].S + 1 == dp[mask][i].S)
dp[mask][i].F = min(dp[mask][i].F, tmp);
}
}
}
}
int ans = 0;
FOR(mask, 1, (1 << n) - 1) FOR(i, 0, n - 1) ans = max(ans, dp[mask][i].S);
cout << ans << "\n";
}
}
namespace subFull {
li dp[MAX_N][MAX_N][2];
long long dist(long long x, long long y) {
if (x > y) swap(x, y);
return min(y - x, x + l - y);
}
void update(li &A, li B, long long newDist, int limit) {
if (newDist <= limit) {
if (B.S + 1 > A.S) A = {newDist, B.S + 1};
else if (B.S + 1 == A.S && newDist < A.F) A.F = newDist;
}
else {
if (B.S > A.S) A = {newDist, B.S};
else if (B.S == A.S && newDist < A.F) A.F = newDist;
}
}
void solve() {
FOR(i, 0, n + 1) FOR(j, 0, n + 1) FOR(k, 0, 1) dp[i][j][k] = {INF, -1};
dp[0][n + 1][0] = dp[0][n + 1][1] = {0, 0};
pos[n + 1] = pos[0] = 0;
FOR(i, 0, n) FOD(j, n + 1, i + 1) {
if (dp[i][j][0].F < INF) {
if (i != n && i + 1 < j) {
long long newDist = dp[i][j][0].F + dist(pos[i], pos[i + 1]);
update(dp[i + 1][j][0], dp[i][j][0], newDist, timeLimit[i + 1]);
}
if (j - 1 > i) {
long long newDist = dp[i][j][0].F + dist(pos[i], pos[j - 1]);
update(dp[i][j - 1][1], dp[i][j][0], newDist, timeLimit[j - 1]);
}
}
if (dp[i][j][1].F < INF) {
if (i != n && i + 1 < j) {
long long newDist = dp[i][j][1].F + dist(pos[j], pos[i + 1]);
update(dp[i + 1][j][0], dp[i][j][1], newDist, timeLimit[i + 1]);
}
if (j - 1 > i) {
long long newDist = dp[i][j][1].F + dist(pos[j], pos[j - 1]);
update(dp[i][j - 1][1], dp[i][j][1], newDist, timeLimit[j - 1]);
}
}
}
int ans = 0;
FOR(i, 0, n) FOR(j, 0, n) FOR(k, 0, 1) if (dp[i][j][k].F < INF) ans = max(ans, dp[i][j][k].S);
cout << ans << "\n";
}
}
void solve() {
cin >> n >> l;
FOR(i, 1, n) cin >> pos[i];
FOR(i, 1, n) cin >> timeLimit[i];
// if (n <= 15) sub2::solve();
subFull::solve();
}
int32_t main() {
if (fopen(task".inp", "r")) {
freopen(task".inp", "r", stdin);
freopen(task".out", "w", stdout);
}
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
bool multitest = 0;
int numTest = 1;
if (multitest) cin >> numTest;
while (numTest--) {
solve();
}
return 0;
}
/* Lak lu theo dieu nhac!!!! */
