// ~~ icebear ~~
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int, int> ii;
typedef pair<int, ii> iii;
template<class T>
bool minimize(T &a, const T &b) {
if (a > b) return a = b, true;
return false;
}
template<class T>
bool maximize(T &a, const T &b) {
if (a < b) return a = b, true;
return false;
}
#define FOR(i,a,b) for(int i=(a); i<=(b); ++i)
#define FORR(i,a,b) for(int i=(a); i>=(b); --i)
#define REP(i, n) for(int i=0; i<(n); ++i)
#define RED(i, n) for(int i=(n)-1; i>=0; --i)
#define MASK(i) (1LL << (i))
#define BIT(S, i) (((S) >> (i)) & 1)
#define mp make_pair
#define pb push_back
#define fi first
#define se second
#define all(x) x.begin(), x.end()
#define task "icebear"
const int MOD = 1e9 + 7;
const int inf = 1e9 + 27092008;
const ll INF = 1e18 + 27092008;
const int N = 200 + 5;
int n, L, X[N], T[N];
ll f[N][N][N][2];
ll dist(int i, int j) {
return min(X[j] - X[i], L - X[j] + X[i]);
}
void init(void) {
cin >> n >> L;
FOR(i, 1, n) cin >> X[i];
FOR(i, 1, n) cin >> T[i];
}
void process(void) {
memset(f, 0x3f, sizeof f);
ll nA = f[0][0][0][0];
f[0][n+1][0][0] = f[0][n+1][0][1] = 0;
X[n + 1] = L;
FOR(i, 0, n) FORR(j, n + 1, i + 1) FOR(k, 0, i + n - j + 1) REP(t, 2) if (f[i][j][k][t] != nA) {
minimize(f[i + 1][j][k][0], f[i][j][k][t] + (t == 0 ? dist(i, i + 1) : dist(i + 1, j)));
minimize(f[i][j - 1][k][1], f[i][j][k][t] + (t == 0 ? dist(i, j - 1) : dist(j - 1, j)));
if (f[i + 1][j][k][0] <= T[i + 1]) minimize(f[i + 1][j][k + 1][0], f[i + 1][j][k][0]);
if (f[i][j - 1][k][1] <= T[j - 1]) minimize(f[i][j - 1][k + 1][1], f[i][j - 1][k][1]);
}
int ans = 0;
FOR(i, 0, n) FOR(k, 0, n) REP(t, 2) {
if (f[i][i + 1][k][t] != nA) maximize(ans, k);
}
cout << ans;
}
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
if (fopen(task".inp", "r")) {
freopen(task".inp", "r", stdin);
freopen(task".out", "w", stdout);
}
int tc = 1;
// cin >> tc;
while(tc--) {
init();
process();
}
return 0;
}
