#include<bits/stdc++.h>
#define IOS ios_base::sync_with_stdio(false);cin.tie();cout.tie();
#define all(x) x.begin(), x.end()
#define int long long
#define pq priority_queue
#define lb lower_bound
#define ub upper_bound
#define pb push_back
#define mset multiset
#define F first
#define S second
using namespace std;
int n;
vector<vector<int > > dp(5001, vector<int >(5001, 0));
vector<vector<int > > psum(5001, vector<int >(5001, 0));
int inv(int up, int val, int p)
{
int cnt = 0;
cnt += psum[up][p] - psum[val - 1][p];
cnt += psum[val - 1][n] - psum[val - 1][p];
return cnt;
}
void solve ()
{
cin >> n;
vector<int > arr(n+1), pos(n+1);
for (int i = 1; i <= n; i++)
{
cin >> arr[i];
pos[arr[i]] = i;
}
dp[1][1] = 0;
psum[1][pos[1]] = 1;
for (int i = 1; i <= n; i++) psum[1][i] += psum[1][i-1];
for (int i = 2; i <= n; i++)
{
dp[i][i] = 1e9;
for (int j = 1; j < i; j++)
{
dp[i][j] = dp[i - 1][j] + inv(i - 1, j, pos[i]);
dp[i][i] = min(dp[i][i], dp[i - 1][j] + inv(i - 1, i, pos[i]));
}
for (int j = 1; j <= i; j++) psum[i][pos[j]]++;
for (int j = 1; j <= n; j++) psum[i][j] += psum[i][j - 1];
}
int ans = 1e9;
for (int i = 1; i <= n; i++) ans = min(ans, dp[n][i]);
cout << ans;
}
signed main(){IOS solve(); return 0;}
