#include <bits/stdc++.h>
#define IO_OP std::ios::sync_with_stdio(0); std::cin.tie(0);
#define F first
#define S second
#define V vector
#define PB push_back
#define EB emplace_back
#define MP make_pair
#define SZ(v) int((v).size())
#define ALL(v) (v).begin(), (v).end()
using namespace std;
typedef long long ll;
typedef pair<int, int> pi;
typedef V<int> vi;
string _reset = "\u001b[0m", _yellow = "\u001b[33m", _bold = "\u001b[1m";
void DBG() { cerr << "]" << _reset << endl; }
template<class H, class...T> void DBG(H h, T ...t) {
cerr << to_string(h);
if(sizeof ...(t)) cerr << ", ";
DBG(t...);
}
#ifdef CHEISSMART
#define debug(...) cerr << _yellow << _bold << "Line(" << __LINE__ << ") -> [" << #__VA_ARGS__ << "]: [", DBG(__VA_ARGS__)
#else
#define debug(...)
#endif
const int INF = 1e9 + 7;
signed main()
{
IO_OP;
int n;
cin >> n;
vi p(n);
for(int i = 0; i < n; i++) {
cin >> p[i];
p[i]--;
}
int ans = INF;
auto go = [&] (vi q) {
vi iq(n);
for(int i = 0; i < n; i++)
iq[q[i]] = i;
vi pp;
for(int i:p)
pp.PB(iq[i]);
int tt = 0;
for(int i = 0; i < n; i++) {
if(pp[i] != i) {
tt++;
}
}
ans = min(ans, tt);
};
vi q(n); iota(ALL(q), 0);
auto ok = [&] (vi a) {
int l = 0, r = n - 1, lb = 0, rb = n - 1;
while(r - l + 1 >= 4) {
if(a[l] != lb && a[l] != rb && a[r] != lb && a[r] != rb)
return false;
if(a[l] == lb)
l++, lb++;
else if(a[l] == rb)
l++, rb--;
else if(a[r] == lb)
r--, lb++;
else
r--, rb--;
}
return true;
};
do {
if(ok(q))
go(q);
} while(next_permutation(ALL(q)));
cout << ans << '\n';
}
