#include<bits/stdc++.h>
using namespace std;
/*for ordered_set
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
#define ordered_set tree<pair<int,int>, null_type,less<pair<int,int>>, rb_tree_tag,tree_order_statistics_node_update>
*/
const long long INFll = (long long) 1e18 + 10;
const int INFii = (int) 1e9 + 10;
typedef long long ll;
typedef int ii;
typedef long double dbl;
#define endl '\n'
#define sc second
#define fr first
#define mp make_pair
#define pb push_back
#define all(x) x.begin(), x.end()
#define maxn 5100
ii n, a[maxn], pos[maxn], dp[maxn], mark[maxn];
ii bit[maxn][maxn], bit1[maxn][maxn];
void att(ii id1, ii id2, ii val) {
for(ii i = id2; i <= n; i+= i&-i) {
bit[id1][i]+= val;
}
}
ii qr(ii id1, ii id2) {
ii val = 0;
for(ii i = id2; i > 0; i-= i&-i) {
val+= bit[id1][i];
}
return val;
}
void att1(ii id1, ii id2, ii val) {
for(ii i = id2; i <= n; i+= i&-i) {
bit1[id1][i]+= val;
}
}
ii qr1(ii id1, ii id2) {
ii val = 0;
for(ii i = id2; i > 0; i-= i&-i) {
val+= bit1[id1][i];
}
return val;
}
ii sol(ii i) {
if(mark[i]) return dp[i];
mark[i] = 1;
ii ans = INFii;
if(i == n) return dp[i] = 0;
for(ii j = 1; j <= n; j++) {
bit[i][j] = 0;
bit1[i][j] = 0;
}
for(ii j = 1; j <= i; j++) {
att(i,pos[j],1);
}
ii ans1 = 0;
for(ii j = i+1; j <= n; j++) {
//colocando o j com os <= i
ans1+= i-qr(i,pos[j]);
//atualizando a parte do j -> j+1
ans1+= j-i-1;
//colocando a mudanca pos[x] > pos[j]
ans1-= j-i-1-qr1(i,pos[j]);
att1(i,pos[j],1);
ans = min(ans, ans1+sol(j));
// cout << i << " " << j << " " << ans1 << " " << sol(j) << endl;
}
return dp[i] = ans;
}
void solve() {
cin >> n;
for(ii i = 1; i <= n; i++) {
cin >> a[i];
pos[a[i]] = i;
}
cout << sol(0) << endl;
}
int main() {
ios::sync_with_stdio(false); cin.tie(0);
// freopen("in.in", "r", stdin);
//freopen("out.out", "w", stdout);
ii tt = 1;
// cin >> tt;
while(tt--) solve();
}
