#include <bits/stdc++.h>
using namespace std;
//#define int long long
#define pi pair<int, int>
#define pii pair<int, pi>
#define fi first
#define se second
#ifdef _WIN32
#define getchar_unlocked _getchar_nolock
#endif
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
struct node{
int s, e, m;
int mx, mn, lazy, val;
node *l, *r;
node(int _s, int _e){
s = _s, e = _e, m = (s + e) >> 1;
if(s != e)l = new node(s, m), r = new node(m+1, e);
mx = mn = lazy = val = 0;
}
void prop(){
if(!lazy)return;
mx += lazy, mn += lazy;
if(s != e)l->lazy += lazy, r->lazy += lazy;
lazy = 0;
}
void upd(int a, int b, int c){
if(a == s && b == e)lazy += c;
else{
if(b <= m)l->upd(a, b, c);
else if(a > m)r->upd(a, b, c);
else l->upd(a, m, c), r->upd(m+1, b, c);
l->prop(), r->prop();
mn= min(l->mn, r->mn);
mx= max(l->mx, r->mx);
}
}
pi qry(int a, int b){
prop();
if(a == s && b == e)return {mn, mx};
if(b <= m)return l->qry(a, b);
else if(a > m)return r->qry(a, b);
else{
pi lft = l->qry(a, m), rgt = r->qry(m+1 ,b);
return {min(lft.fi, rgt.fi), max(lft.se, rgt.se)};
}
}
}*lft, *rgt;
vector <int> occ[500005];
int sequence(int N, vector <int> A){
for(int i=0;i<N;i++)occ[A[i]].push_back(i);
int lo = 2, hi = N, ans = 1;
while(lo <= hi){
lft = new node(0, N);
rgt = new node(0, N);
int mid = (lo + hi) >> 1;
for(int i=0;i<N;i++){
lft->upd(i, N - 1, 1);
rgt->upd(0, i, 1);
}
bool f = 0;
for(int i=1;i<=N;i++){
for(auto j : occ[i]){
lft->upd(j, N - 1, -1);
rgt->upd(0, j, -1);
}
for(int j = mid - 1; j < (int)occ[i].size(); j++){
int l = occ[i][j - (mid - 1)], r = occ[i][j];
pi tmp = rgt->qry(0, l), tmp2 = lft->qry(r, N - 1);
pi ref = rgt->qry(l, l), ref2 = lft->qry(r, r);
tmp.fi -= ref.fi; tmp.se -= ref.se; tmp2.fi -= ref2.fi; tmp2.se -= ref2.se;
tmp.fi += tmp2.fi;
tmp.se += tmp2.se;
int val = lft->qry(r - 1, r - 1).fi - lft->qry(l, l).fi;
int mn = val + tmp.fi, mx = val + tmp.se;
//if(mid == 3)cout << val << ' ' << mx << ' ' << mn << '\n';
if(mx >= -mid && mn <= mid)f = 1;
}
for(auto j : occ[i]){
lft->upd(j, N - 1, -1);
rgt->upd(0, j, -1);
}
}
if(f)ans = mid, lo = mid + 1;
else hi = mid - 1;
}
return ans;
}
