#include <bits/stdc++.h>
#include "sequence.h"
using namespace std;
int sequence(int n, vector<int> a) {
vector<vector<int>> pos(n + 1);
for (int i = 0; i < n; i++) {
pos[a[i]].push_back(i);
}
vector<vector<int>> p(4, vector<int>(n + 1));
for (int x = 1; x <= 3; x++) {
for (int i = 0; i < n; i++) {
p[x][i + 1] = p[x][i] + (a[i] == x);
}
}
auto good = [&](int k, int l, int r) {
int x = 0, y = 0, z = 0;
for (int i = 1; i <= 3; i++) {
int s = p[i][r + 1] - p[i][l];
if (k < i) {
x += s;
} else if (k == i) {
y += s;
} else {
z += s;
}
}
return max(x, z) <= r - l + 1;
};
int ans = 0;
for (int k = 1; k <= 3; k++) {
int l = 0, r = pos.size() + 1;
while (l + 1 < r) {
int m = (l + r) / 2;
bool ok = 0;
for (int i = 0; i + m <= pos[k].size(); i++) {
if (good(k, pos[k][i], pos[k][i + m - 1])) {
ok = 1;
break;
}
}
if (ok) {
l = m;
} else {
r = m;
}
}
ans = max(ans, l);
}
return ans;
}
