#include<iostream>
#include<vector>
#include<algorithm>
#include<utility>
#define INF 10000000000000000
#define int long long
using namespace std;
signed main() {
ios::sync_with_stdio(false);
cin.tie(0);
int n;
cin >> n;
vector<int>v(n+5);
vector<int>pos(n+5);
//vector<vector<int> >arr(n+5, vector<int>(n+5));
for (int i = 1 ; i <= n ; i++) {
cin >> v[i];
pos[v[i]] = i;
}
vector<vector<int> >front(n+5, vector<int>(n+5, 0));
//" front[i][j] -> 1~j有幾個在i前"
for (int i = 1 ; i<= n ; i++) {
front[i][0] = 0;
for (int j = 1 ; j <= n ; j++) {
if (pos[j] < pos[i]) front[i][j] = front[i][j-1] + 1;
else front[i][j] = front[i][j-1];
}
}
vector<int>dp(n, INF);
vector<vector<int> >cost(n+5, vector<int>(n+5));
//cost(i-1, j) :[... ][j ...] [ i-1 i-2 ... j+1] ...
//cost(i, j) : [... ][j ...] [ i i-1 ... j+1] ...
//cost(i+1, j): [... ][j ...] [ i+1 i ... j+1] ...
//"cost[i+1][j] = cost[i][j] + (j+1~n 在i+1前) - (j+1~i 在i+1後) "// i > j
//"cost[i][j] = cost[i-1][j] + (j+1~n 在i前) - (j+1~i-1 在i後) "// i > j
vector<int>ans(n+5, INF);
ans[0] = 0;
for (int j = 0 ; j <= n ; j++) {
//cost[i][0] = 0;
cost[j+1][j] = ans[j] + (front[j+1][n] - front[j+1][j]);
ans[j+1] = min(ans[j+1], cost[j+1][j]);
//cout << j << " " << ans[j] << "\n";
//cout << j+1 << " " << j << " " << cost[j+1][j] << "\n";
for (int i = j+2 ; i <= n ; i++) {
// j j-1 ... [i i-1 ... j+1]
cost[i][j] = cost[i-1][j] + (front[i][n] - front[i][j]) - ((i-j-1) - (front[i][i-1] - front[i][j]) );
ans[i] = min(ans[i], cost[i][j]);
//cout << i << " " << j << " " << cost[i][j] << "\n";
}
}
cout << ans[n] << "\n";
for (int i = 1 ; i <= n ; i++) {
for (int j = 0 ; j < i ; j++) {
dp[i] = min(dp[i], dp[j] + cost[i][j]);
}
}
}
