#include <bits/stdc++.h>
using namespace std;
#define fr first
#define sc second
#define all(x) (x).begin(), (x).end()
const int MOD = 1e9 + 7;
const int MAXN = 2e2 + 5;
const long long INF = 1e18 + 5;
int n, d;
int dp[205][205][205][2];
vector<int> t(MAXN), x(MAXN);
int dist(int a, int b) {
if(b >= a) return min(x[b] - x[a], d - (x[b] - x[a]));
return min(x[a] - x[b], d - (x[a] - x[b]));
}
int32_t main() {
ios::sync_with_stdio(false);
cin.tie(NULL);
cin >> n >> d;
for(int i = 1; i <= n; i++) cin >> x[i];
for(int i = 1; i <= n; i++) cin >> t[i];
t[0] = -1;
x[0] = 0;
for(int l = 0; l <= n; l++) for(int r = 0; r <= n; r++) {
for(int qtd = 0; qtd <= n; qtd ++) {
dp[l][r][qtd][0] = MOD;
dp[l][r][qtd][1] = MOD;
}
}
for(int l = 0; l <= n; l++) for(int r = l; r <= n; r++) {
dp[l][r][0][0] = min(dp[l][r][0][0], dist(0,r) + dist(r,l));
dp[l][r][0][1] = min(dp[l][r][0][1], dist(0,l) + dist(l,r));
}
for(int qtd = 1; qtd <= n; qtd++) {
for(int sz = 1; sz <= n; sz++) {
for(int l = 0; l <= n; l++) {
int r = (l + sz - 1) % (n+1);
int nl, nr;
nl = (l < n ? l + 1 : 0);
nr = (r > 0 ? r - 1 : n);
dp[l][r][qtd][0] = min(dp[l][r][qtd][0], dp[nl][r][qtd][0] + dist(nl, l));
if(dp[nl][r][qtd-1][0] + dist(nl, l) <= t[l]) {
dp[l][r][qtd][0] = min(dp[l][r][qtd][0], dp[nl][r][qtd-1][0] + dist(nl, l));
}
if(dp[nl][r][qtd-1][1] + dist(r, l) <= t[l]) {
dp[l][r][qtd][0] = min(dp[l][r][qtd][0], dp[nl][r][qtd-1][1] + dist(r, l));
}
dp[l][r][qtd][1] = min(dp[l][r][qtd][1], dp[l][nr][qtd][1] + dist(nr, r));
if(dp[l][nr][qtd-1][1] + dist(nr, r) <= t[r]) {
dp[l][r][qtd][1] = min(dp[l][r][qtd][1], dp[l][nr][qtd-1][1] + dist(nr, r));
}
if(dp[l][nr][qtd-1][0] + dist(l, r) <= t[r]) {
dp[l][r][qtd][1] = min(dp[l][r][qtd][1], dp[l][nr][qtd-1][0] + dist(l, r));
}
}
}
}
int ans = 0;
for(int l = 0; l <= n; l++) for(int r = 0; r <= n; r++) {
for(int qtd = 0; qtd <= n; qtd ++) {
if(dp[l][r][qtd][0] < MOD || dp[l][r][qtd][1] < MOD) ans = max(ans, qtd);
}
}
cout << ans << "\n";
return 0;
}
