#include <bits/stdc++.h>
using namespace std;

#define rep(i, a, b) for(int i = a; i < (b); ++i)
#define trav(a, x) for(auto& a : x)
#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()
#define subnb true
#define Lnb true
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef vector<int> vi;

const int N = (int)4e5 + 50;
const int INF = (int)1e9;
#define lson(x) 2*x+1
#define rson(x) 2*x+2


struct node {
    ll mx, cnt;

};

node merge(node L, node R) {
    return {max(L.mx + R.cnt * 2, R.mx), L.cnt + R.cnt};
}

struct Tree {
    node dat[4 * N];
    void init(int x, int l, int r) {
        if(l == r) {dat[x] = {-INF, 0}; return ;}
        int mid = (l + r) / 2;
        init(lson(x), l, mid);
        init(rson(x), mid + 1, r);
        dat[x] = merge(dat[lson(x)], dat[rson(x)]);
    }
    void update(int pos, int x, int l, int r, node val) {
        if(l == r) {dat[x] = val; return ;}
        int mid = (l + r) / 2;
        if(pos <= mid) update(pos, lson(x), l, mid, val);
        else update(pos, rson(x), mid + 1, r, val);
        dat[x] = merge(dat[lson(x)], dat[rson(x)]);
    }
    node query(int a, int b, int x, int l, int r) {
        if(r < a || b < l) return {-INF, 0};
        int mid = (l + r) / 2;
        if(a <= l && r <= b) return dat[x];
        else return merge(query(a, b, lson(x), l, mid),
                          query(a, b, rson(x), mid + 1, r));
    }
} tree;

int n;
int a[N];
vector<pii> ps;
int in[N];
int pf = 0;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(NULL);

    cin >> n;
    n++;
    rep(i, 0, n) cin >> a[i], ps.push_back({a[i], i});
    sort(all(ps));
    tree.init(0, 0, n - 1);
    ll res = 0;
    int c = 0;
    for (auto p : ps) {
        c++;
        tree.update(p.second, 0, 0, n - 1, node{p.second + (p.second % 2 == 0), 1});
        in[p.second] = 1;
        while(pf < n && in[pf]) {
            tree.update(pf, 0, 0, n - 1, {-INF, 0});
            pf++;
        }
//        if(c == 0) {
//            continue;
//        }
//        cout << pf << endl;
//
//        cout << p.first << " " << tree.dat[0].mx - (c - 1) << endl;

        res = max(res, tree.dat[0].mx - (c - 1));
    }
    cout << res << endl;



}