#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pb push_back
#define ff first
#define sd second
#define debug(x) cerr << #x << "----> " << x << endl;
//#pragma GCC optimize("unroll-loops")
//#pragma GCC optimize("Ofast")
//#pragma GCC optimize("O3")
const int mxN = 1e6 + 5;
ll n,a[mxN];
//9
//1 1 2 3 4 3 2 1 1
struct segtree{
vector<ll> mn,mx,v1,b;
ll sz = 1,inf = 1e9;
void init(){
while(sz < n + 5) sz *= 2;
v1.assign(2 * sz, 0LL);
mn.assign(2 * sz, 0LL);
mx.assign(2 * sz, 0LL);
b.assign(n + 5, 0LL);
}
void f(ll x){
mx[x] += v1[x];
mn[x] += v1[x];
if(x < sz - 1){
v1[2 * x + 1] += v1[x];
v1[2 * x + 2] += v1[x];
}
v1[x] = 0;
}
void set(ll val, ll l, ll r, ll x, ll lx, ll rx){
f(x);
if(lx >= r or rx <= l) return;
if(lx >= l and rx <= r){
v1[x] += val;
f(x);
return;
}
ll mid = lx + (rx - lx) / 2;
set(val, l, r, 2 * x + 1, lx, mid);
set(val, l, r, 2 * x + 2, mid, rx);
mx[x] = max(mx[2 * x + 1], mx[2 * x + 2]);
mn[x] = min(mn[2 * x + 1], mn[2 * x + 2]);
}
void set(ll val, ll i){
set(val - b[i], i, n + 1, 0, 0, sz);
b[i] = val;
}
pair<ll,ll> find(ll l, ll r, ll x, ll lx, ll rx){
f(x);
if(lx >= r or rx <= l) return {1e9, -1e9};
if(lx >= l and rx <= r) return {mn[x], mx[x]};
ll mid = lx + (rx - lx) / 2;
pair<ll,ll> k = find(l, r, 2 * x + 1, lx, mid),k1 = find(l, r, 2 * x + 2, mid, rx);
return {min(k.ff, k1.ff), max(k.sd, k1.sd)};
}
pair<ll,ll> find(ll l, ll r){
return find(l, r, 0, 0, sz);
}
};
int main(){
ios::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
cin >> n;
segtree s,s1,s2;
s.init();
s1.init();
s2.init();
vector<ll> v[n + 1];
for(int i = 1; i <= n; i++){
cin >> a[i];
v[a[i]].pb(i);
s.set(1, i);
s1.set(1, i);
s2.set(1, i);
}
ll ans = 1;
for(int i = 1; i <= n; i++){
ll r1 = 0;
vector<ll>& vv = v[i];
for(auto it : vv){
s.set(0, it);
s2.set(-1, it);
}
// s.set(-2, 1);
for(int l1 = 0; l1 < vv.size() and r1 < vv.size(); l1++){
bool ok = false;
int l = vv[l1],r = vv[r1];
// s.set(1, r);
s2.set(0, r);
pair<ll,ll> x = s.find(0, l),y = s.find(r, n + 1);
ll sz = r1 - l1 + 1;
if(x.sd <= y.sd){
if(y.ff - sz <= x.sd) ok = true;
else if(s2.find(r, n + 1).ff - sz <= x.sd) ok = true;
}
else{
if(x.ff - sz <= y.sd) ok = true;
else if(x.ff - sz <= s1.find(r, n + 1).sd) ok = true;
}
// cout << i << ' ' << l << ' ' << r << "(" << ok << ")" << "---> ";
// for(int i1 = 0; i1 <= n; i1++) cout << s.find(i1, i1 + 1).ff << ' '; cout << '\n';
// cout << "-----------------. " << x.ff << ' ' << x.sd << ' ' << y.ff << ' ' << y.sd<< '\n';
r1++;
if(ok){
ans = max(ans, r1 - l1);
l1--;
continue;
}
s.set(0, l);
s1.set(0, l);
s2.set(0, l);
}
for(auto it : vv){
s.set(-1, it);
s1.set(-1, it);
s2.set(-1, it);
}
}
cout << ans;
}
