#include <vector>
#include <deque>
#include <iostream>
using namespace std;
typedef long long ll;

int main(){
    ios_base::sync_with_stdio(false);
    int n;
    cin >> n;

    vector<int> v(n);
    for(int i = 0; i < n; i++) {
        cin >> v[i];
    }
    bool pre_ok = true;
    for(int i = 1; i < n; i++) {
        if(v[i] < v[i - 1]) {
            pre_ok = false;
            break;
        }
    }
    if(pre_ok) {
        cout << 0 << endl;
        return 0;
    }

    for(int rounds = 1; rounds <= n; rounds++) {
        if(rounds % 2 == 1) {
            for(int i = 0; i < n; i += 2) {
                if(i + 1 < n and v[i] > v[i + 1]) {
                    swap(v[i], v[i + 1]);
                }
            }
        }
        else {
            for(int i = 1; i < n; i += 2) {
                if(i + 1 < n and v[i] > v[i + 1]) {
                    swap(v[i], v[i + 1]);
                }
            }
        }

        bool ok = true;
        for(int i = 1; i < n; i++) {
            if(v[i] < v[i - 1]) {
                ok = false;
                break;
            }
        }
        if(ok) {
            cout << rounds << endl;
            break;
        }
    }
    return 0;
}