#include "sequence.h"
#include <bits/stdc++.h>
using namespace std;
int N;
int miin[500100 * 4];
int maax[500100 * 4];
int lazy[500100 * 4];
int miin1[500100 * 4];
int maax1[500100 * 4];
int lazy1[500100 * 4];
vector<int> in[500100];
vector<int> sat;
void build(int i, int s, int e, int *miin, int *maax, int *lazy){
miin[i] = - e - 1;
maax[i] = - s - 1;
lazy[i] = 0;
if(s != e){
int m = (s + e + 2)/2 - 1;
build(i * 2, s, m, miin, maax, lazy);
build(i * 2 + 1, m + 1, e, miin, maax, lazy);
}
}
void update(int i, int s, int e, int S, int *miin, int *maax, int *lazy){
if(S <= s){
miin[i] += 2;
maax[i] += 2;
lazy[i] += 2;
return;
}
int m = (s + e + 2)/2 - 1;
update(i * 2 + 1, m + 1, e, S, miin, maax, lazy);
if(S <= m){
update(i * 2, s, m, S, miin, maax, lazy);
}
miin[i] = min(miin[i * 2], miin[i * 2 + 1]) + lazy[i];
maax[i] = max(maax[i * 2], maax[i * 2 + 1]) + lazy[i];
}
pair<int,int> query(int i, int s, int e, int S, int E, int *miin, int *maax, int *lazy){
if(S <= s && e <= E){
return make_pair(miin[i],maax[i]);
}
int m = (s + e + 2)/2 - 1;
pair<int,int> ii,ii1;
if(S <= m && m < E){
ii = query(i * 2, s, m, S, E, miin, maax, lazy);
ii1 = query(i * 2 + 1, m + 1, e, S, E, miin, maax, lazy);
ii.first = min(ii.first, ii1.first) + lazy[i];
ii.second = max(ii.second, ii1.second) + lazy[i];
}
else if(S <= m){
ii = query(i * 2, s, m, S, E, miin, maax, lazy);
ii.first = ii.first + lazy[i];
ii.second = ii.second + lazy[i];
}
else{
ii = query(i * 2 + 1, m + 1, e, S, E, miin, maax, lazy);
ii.first = ii.first + lazy[i];
ii.second = ii.second + lazy[i];
}
return ii;
}
int sequence(int N, std::vector<int> lst) {
for(int i = 0; i < N; i++){
in[lst[i]].push_back(i);
}
build(1,-1,N-1,miin1,maax1,lazy1);
build(1,-1,N-1,miin,maax,lazy);
bool flag = false;
int ans = 0;
for(int i = 1; i <= N; i++){
sat.clear();
sat.push_back(-1);
for(int j = 0; j < in[i].size(); j++){
sat.push_back(in[i][j]);
}
sat.push_back(N);
for(int j = 0; j < in[i].size() ; j++){
update(1,-1,N-1,in[i][j],miin,maax,lazy);
}
for(int j = 1; j <= in[i].size(); j++){
int small = query(1, -1, N - 1, -1, sat[j] - 1, miin, maax, lazy).first;
int big1 = query(1, -1, N - 1, -1, sat[j] - 1, miin1, maax1, lazy1).second;
int l,r,m,s,e;
int eye;
eye = 1;
l = sat[j];
r = N - 1;
s = -1;
e = N - 1;
int lacy = 0;
int lacy1 = 0;
while(s != e){
m = (s + e)/2;
lacy += lazy[eye];
lacy1 += lazy1[eye];
if(m < l){
s = m + 1;
eye = eye * 2 + 1;
continue;
}
if((maax[eye * 2 + 1] + lacy - small) * (long long int)(miin1[eye * 2 + 1] + lacy1 - big1) <= 0){
s = m + 1;
eye = eye * 2 + 1;
continue;
}
else{
e = m;
eye = eye * 2;
}
}
auto it = upper_bound(sat.begin(),sat.end(),s);
it--;
ans = max(ans,(int)(it - sat.begin()) - j + 1);
}
for(int j = 0; j < in[i].size() ; j++){
update(1,-1,N-1,in[i][j],miin1,maax1,lazy1);
}
}
return ans;
}
