//Sylwia Sapkowska
#include <bits/stdc++.h>
#pragma GCC optimize("O3", "unroll-loops")
using namespace std;
void __print(int x) {cerr << x;}
void __print(long long x) {cerr << x;}
void __print(long double x) {cerr << x;}
void __print(char x) {cerr << "'" << x << "'";}
void __print(const char *x) {cerr << '"' << x << '"';}
void __print(const string &x) {cerr << '"' << x << '"';}
void __print(bool x) {cerr << (x ? "true" : "false");}
template<typename T, typename V>
void __print(const pair<T, V> &x) {cerr << '{'; __print(x.first); cerr << ", "; __print(x.second); cerr << '}';}
template<typename T>
void __print(const T &x) {int f = 0; cerr << '{'; for (auto &i: x) cerr << (f++ ? ", " : ""), __print(i); cerr << "}";}
void _print() {cerr << "]\n";}
template <typename T, typename... V>
void _print(T t, V... v) {__print(t); if (sizeof...(v)) cerr << ", "; _print(v...);}
#ifdef LOCAL
#define debug(x...) cerr << "[" << #x << "] = ["; _print(x)
#else
#define debug(x...)
#endif
#define int long long
typedef pair<int, int> T;
const int oo = 1e18, oo2 = 1e9+7, K = 30;
const int mod = 998244353;
void ckmin(int &a, int b){
a = min(a, b);
}
void solve(){
int n, all; cin >> n >> all;
vector<int>x(n+2), t(n+2);
for (int i = 1; i<=n; i++) cin >> x[i];
for (int i = 1; i<=n; i++) cin >> t[i];
t[0] = oo;
t[n+1] = oo;
int ans = 0;
vector dp(n+3, vector<vector<vector<int>>>(n+3, vector<vector<int>>(n+3, vector<int>(2, oo))));
dp[0][0][0][0] = dp[0][0][0][1] = 0;
auto nxt = [&](int a){
return (a+1)%(n+1);
};
auto prev = [&](int a){
return a ? a - 1 : n;
};
auto dist = [&](int i, int j){
int y = abs(x[i] - x[j]);
return min(y, all-y);
};
for (int len = 2; len <= n+1; len++){
// if (len > 3) break;
for (int l = 0, r = len-1; l <= n; l++, r = nxt(r)){
for (int ret = 0; ret <= n; ret++){
int d;
//dp[l][r][ret][rep]
//[l+1, r]
int L = nxt(l);
int R = prev(r);
d = dist(L, l);
int get = (dp[L][r][ret][0] + d <= t[l]);
ckmin(dp[l][r][ret+get][0], dp[L][r][ret][0] + d);
d = dist(l, r);
get = (dp[L][r][ret][1] + d <= t[l]);
ckmin(dp[l][r][ret+get][0], dp[L][r][ret][1] + d);
//[l, r-1]
d = dist(R, r);
get = (dp[l][R][ret][1] + d <= t[r]);
ckmin(dp[l][r][ret+get][1], dp[l][R][ret][1] + d);
d = dist(l, r);
get = (dp[l][R][ret][0] + d <= t[r]);
ckmin(dp[l][r][ret + get][1], dp[l][R][ret][0] + d);
}
}
}
for (int len = 2; len <= n+1; len++){
for (int l = 0, r = len-1; l <= n; l++, r = nxt(r)){
for (int ret = 0; ret <= n; ret++){
if (dp[l][r][ret][0] != oo || dp[l][r][ret][1] != oo){
debug(l, r, ret, dp[l][r][ret][0], dp[l][r][ret][1]);
ans = max(ans, ret);
}
}
}
}
cout << ans << "\n";
}
/*
//dp[l][k][x] --> //dp[l][r][y]
debug(k);
for (int rep = 0; rep < 2; rep++){
int from = (rep ? k : l);
for (int rep2 = 0; rep2 < 2; rep2++){
int to = (rep ? r : l);
int xx = dp[l][k][rep].second + dist(from, to);
int get = (xx <= t[to]);
ckmax(dp[l][r][rep2], {dp[l][k][rep].first+get, xx});
}
int from2 = (rep ? r : k);
for (int rep2 = 0; rep2 < 2; rep2++){
int to = (rep ? r : l);
int xx = dp[k][r][rep].second + dist(from2, to);
int get = (xx <= t[to]);
ckmax(dp[l][r][rep2], {dp[k][r][rep].first+get, xx});
}
}
if (k == r) break;
}
debug(l, r, dp[l][r][0], dp[l][r][1]);
// if (l == 0 && r == 1) exit(0);
*/
int32_t main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int t = 1;
//cin >> t;
while (t--) solve();
return 0;
}
