#include <bits/stdc++.h>
#define pii pair<int, int>
#define fi first
#define se second
using namespace std;
const int N = 5e5 + 5;
int n, seg[N << 2][2];
int lazy[N << 2], ans;
vector<int> P[N];
void build(int id, int l, int r){
if (l == r){
seg[id][0] = seg[id][1] = l;
return;
}
int mid = l + ((r - l) >> 1);
build(id << 1, l, mid); build((id << 1) | 1, mid + 1, r);
seg[id][0] = min(seg[id << 1][0], seg[(id << 1) | 1][0]);
seg[id][1] = max(seg[id << 1][1], seg[(id << 1) | 1][1]);
}
void down(int id){
int &v = lazy[id];
seg[id << 1][0] += v; seg[id << 1][1] += v;
seg[(id << 1) | 1][0] += v; seg[(id << 1) | 1][1] += v;
lazy[id << 1] += v; lazy[(id << 1) | 1] += v;
v = 0;
}
void update(int id, int l, int r, int u, int v, int val){
if (r < u || v < l) return;
if (u <= l && r <= v){
seg[id][0] += val;
seg[id][1] += val;
lazy[id] += val;
return;
}
if (lazy[id]) down(id);
int mid = l + ((r - l) >> 1);
update(id << 1, l, mid, u, v, val);
update((id << 1) | 1, mid + 1, r, u, v, val);
seg[id][0] = min(seg[id << 1][0], seg[(id << 1) | 1][0]);
seg[id][1] = max(seg[id << 1][1], seg[(id << 1) | 1][1]);
}
pii get(int id, int l, int r, int u, int v){
if (r < u || v < l) return {N, -N};
if (u <= l && r <= v) return {seg[id][0], seg[id][1]};
if (lazy[id]) down(id);
int mid = l + ((r - l) >> 1);
pii t1 = get(id << 1, l, mid, u, v),
t2 = get((id << 1) | 1, mid + 1, r, u, v);
return {min(t1.fi, t2.fi), max(t1.se, t2.se)};
}
bool check(pii x, pii y, int val){
if (x > y) swap(x, y);
return y.fi - x.se <= val;
}
int main(){
ios_base::sync_with_stdio(0); cin.tie(0);
cin >> n;
for (int i = 1, x; i <= n; ++i) cin >> x, P[x].push_back(i);
build(1, 0, n);
for (int i = 1; i <= n; ++i)
if ((int)P[i].size()){
for (int x: P[i])
update(1, 0, n, x, n, -1);
int j = 0;
for (int k = 0; k < (int)P[i].size(); ++k){
pii cur = get(1, 0, n, 0, P[i][k] - 1);
j = max(j, k);
while (j < (int)P[i].size() && check(cur, get(1, 0, n, P[i][j], n), j - k + 1))
++j;
ans = max(ans, j - k);
}
for (int x: P[i])
update(1, 0, n, x, n, -1);
}
cout << ans;
}
