#include<bits/stdc++.h>
#define ll long long
#define ldb long double
#define fi first
#define se second
#define sza(a) (int)a.size()
#define pir pair<int,int>
#define pirll pair<ll,ll>
using namespace std;
const int maxn = 8e3 + 5;
int a[maxn],pos[maxn];
namespace sub1{
bool check(int n){
return n <= 7;
}
bool good(const vector <int> &vec){
int n = vec.size(),M = 0,m = n + 1;
for (int l = 0 ; l < n - 2 ; l++){
M = 0;m = n + 1;
for (int r = l + 2 ; r < n ; r++){
M = max(M,vec[r - 1]);
m = min(m,vec[r - 1]);
if (M > max(vec[l],vec[r]) && m < min(vec[l],vec[r]))
return 0;
}
}
return 1;
}
void solve(int n){
vector <int> vec(n);
for (int i = 0 ; i < n ; i++) vec[i] = i + 1;
int res = n;
do{
int tmp = 0;
if (good(vec)){
for (int i = 1 ; i <= n ; i++)
tmp += (a[i] != vec[i - 1]);
res = min(res,tmp);
}
} while (next_permutation(vec.begin(),vec.end()));
cout << res;
}
}
int main(){
ios_base::sync_with_stdio(false);
cin.tie(0);cout.tie(0);
int n;
cin >> n;
for (int i = 1 ; i <= n ; i++) cin >> a[i];
sub1::solve(n);
return 0;
}
