#include <bits/stdc++.h>
using namespace std;
#ifdef ngu
#include "debug.h"
#else
#define debug(...) 42
#endif
#define int long long
const int N = 205;
int n, l;
int x[N], t[N];
int dp[N][N][N][2];
template<class A, class B>
bool mini(A &a, const B &b) {
return a > b ? (a = b), true : false;
}
int dis(int a, int b) {
if (x[a] > x[b]) {
swap(a, b);
}
return min(x[b] - x[a], x[a] + l - x[b]);
}
signed main() {
ios::sync_with_stdio(false);
cin.tie(0);
#ifdef ngu
freopen("test.inp", "r", stdin);
freopen("test.out", "w", stdout);
#endif
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, 0x3f, sizeof(dp));
const int INF = (int) 1e18;
dp[0][0][0][0] = 0;
int res = 0;
for (int len = 0; len < n; ++len) {
for (int L = 0; L <= len; ++L) {
int R = len - L;
for (int cnt = 0; cnt <= len; ++cnt) {
for (int j = 0; j < 2; ++j) {
if (dp[L][R][cnt][j] < INF) {
res = max(res, cnt);
int T = dp[L][R][cnt][j];
int cur = j == 0 ? n + 1 - L : R;
if (T + dis(cur, n - L) <= t[n - L]) {
res = max(res, cnt + 1);
mini(dp[L + 1][R][cnt + 1][0], T + dis(cur, n - L));
} else {
mini(dp[L + 1][R][cnt][0], T + dis(cur, n - L));
}
if (T + dis(cur, R + 1) <= t[R + 1]) {
res = max(res, cnt + 1);
mini(dp[L][R + 1][cnt + 1][1], T + dis(cur, R + 1));
} else {
mini(dp[L][R + 1][cnt][1], T + dis(cur, R + 1));
}
}
}
}
}
}
cout << res;
}
