// Created by Armin on 1/20/2025.

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pp = pair<int, int>;

int main() {
    ios_base::sync_with_stdio(false); cin.tie(0);
    
    int n; cin >> n;
    vector<int> v(n);
    map<int, int> where;
    for (int i = 0; i < n; i++) {
      cin >> v[i];
      where[v[i]] = i;
    }

    int current1 = n / 2 + 1;
    int next1 = current1 + 1;
    while (next1 <= n && where[current1] < where[next1]) {
      current1 = next1;
      next1++;
    }

    int current2 = n / 2 + 1;
    int next2 = current2 - 1;
	while (next2 > 0 && where[current2] > where[next2]) {
		current2 = next2;
		next2--;
	}
    cout << max((n - current1) * 2, (current2 - 1) * 2 - 1) << endl;
    
    return 0;
}