// Wounds should become scars but I'm cracked instead U+1FAE0
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<ll, ll> pll;
#define all(x) (x).begin(),(x).end()
#define X first
#define Y second
#define sep ' '
#define endl '\n'
#define debug(x) cerr << #x << ": " << x << endl;
const ll MAXN = 1e6 + 10;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
int n, T[MAXN], P[MAXN], F[MAXN], ind[MAXN];
inline void rand_perm() {
int l = 1, r = n;
int fl = 1, fr = n;
for (int i = 1; i <= n; i++) {
int x = (rng() % 2 ? fr-- : fl++);
int y = (rng() % 2 ? r-- : l++);
T[y] = x;
}
}
inline int distance() {
for (int i = 1; i <= n; i++)
ind[P[i]] = i;
for (int i = 1; i <= n; i++)
F[ind[T[i]]] = i;
int ans = 0;
for (int i = 1; i <= n; i++)
if (F[i] != i)
ans++;
return ans;
}
int main() {
ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
cin >> n;
for (int i = 1; i <= n; i++) cin >> P[i];
int fuck = 10000000 * 13 / n;
int ans = n;
while (fuck--) {
rand_perm();
ans = min(ans, distance());
}
cout << ans << endl;
return 0;
}
