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| #include <cstdio>
#include <vector>
#include <algorithm>
#define pb push_back
#define fi first
#define se second
using namespace std;
template <class Type>
void read (Type &x)
{
char c;
bool flag = false;
while ((c = getchar()) < '0' || c > '9')
c == '-' && (flag = true);
x = c - '0';
while ((c = getchar()) >= '0' && c <= '9')
x = (x << 1) + (x << 3) + c - '0';
flag && (x = ~x + 1);
}
template <class Type, class ...rest>
void read (Type &x, rest &...y) { read(x), read(y...); }
template <class Type>
void write (Type x)
{
x < 0 && (putchar('-'), x = ~x + 1);
x > 9 && (write(x / 10), 0);
putchar('0' + x % 10);
}
typedef pair <int, int> PII;
const int N = 5e4 + 10, M = 31;
int n, m, idx, ans, w[N], rt[N], f[N], g[N];
struct Node { int s[2], v; } tr[N * (M + 1)];
namespace Init
{
int v[N];
PII tr[N];
void chkmax (PII &x, int k)
{
if (!x.fi || (k && k > x.fi)) x.se = x.fi, x.fi = k;
else if (!x.se || (k && k > x.se)) x.se = k;
}
void chkmin (PII &x, int k)
{
if (!x.fi || (k && k < x.fi)) x.se = x.fi, x.fi = k;
else if (!x.se || (k && k < x.se)) x.se = k;
}
void add (int x, int k, void (*chk)(PII &x, int k))
{
for (; x; x -= x & -x)
chk(tr[x], k);
}
int ask (int x, void (*chk)(PII &x, int k))
{
PII res { 0, 0 };
for (; x <= m; x += x & -x)
chk(res, tr[x].fi), chk(res, tr[x].se);
return res.fi ? res.se : -1;
}
void main ()
{
vector <int> ws;
for (int i = 1; i <= n; ++i) ws.pb(w[i]);
sort(ws.begin(), ws.end());
m = ws.erase(unique(ws.begin(), ws.end()), ws.end()) - ws.begin();
for (int i = 1; i <= n; ++i)
v[i] = upper_bound(ws.begin(), ws.end(), w[i]) - ws.begin();
for (int i = 1; i <= n; ++i)
f[i] = ask(v[i] + 1, chkmax), add(v[i], i, chkmax);
for (int i = 1; i <= m; ++i) tr[i] = { 0, 0 };
for (int i = n; i; --i)
g[i] = ask(v[i] + 1, chkmin), add(v[i], i, chkmin);
}
}
void insert (int &x, int k, int t = M - 1)
{
tr[++idx] = tr[x], x = idx;
++tr[x].v;
if (!~t) return;
insert(tr[x].s[k >> t & 1], k, t - 1);
}
int query (int x, int y, int k, int t = M - 1)
{
if (!~t) return 0;
int c = k >> t & 1;
if (tr[tr[y].s[c ^ 1]].v > tr[tr[x].s[c ^ 1]].v)
return query(tr[x].s[c ^ 1], tr[y].s[c ^ 1], k, t - 1) | 1 << t;
return query(tr[x].s[c], tr[y].s[c], k, t - 1);
}
int main ()
{
read(n);
for (int i = 1; i <= n; ++i)
read(w[i]), insert(rt[i] = rt[i - 1], w[i]);
Init::main();
for (int i = 1; i <= n; ++i) if (~f[i] || ~g[i])
ans = max(ans, query(rt[f[i] > 0 ? f[i] : 0], rt[g[i] > 0 ? g[i] - 1 : n], w[i]));
write(ans);
return 0;
}
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