#include <iostream>
using namespace std;
int inv[5001][5001];
int main()
{
int N;
cin >> N;
int H[N+1], pos[N+1];
for(int i = 1; i <= N; i++) cin >> H[i];
for(int i = 1; i <= N; i++) pos[ H[i] ] = i;
int lowct[N+1][N+1]; //number of positions <= j with value greater than i
for(int i = 1; i <= N; i++)
{
lowct[i][0] = 0;
for(int j = 1; j <= N; j++)
{
lowct[i][j] = lowct[i][j-1] + (pos[j] > pos[i]);
}
}
for(int i = 1; i <= N; i++)
{
inv[i][i] = 0;
for(int j = i+1; j <= N; j++)
{
inv[i][j] = inv[i][j-1] + (lowct[j][j] - lowct[j][i-1]);
}
}
for(int j = 0; j <= N; j++) inv[0][j] = inv[1][j];
// for(int i = 1; i <= N; i++)
// {
// cout << pos[i] << ' ';
// }
// cout << '\n';
int dp[N+1];
dp[0] = 0;
for(int i = 1; i <= N; i++)
{
dp[i] = 1e9;
for(int l = 1; l <= i; l++)
{
dp[i] = min(dp[i], dp[i-l] + l*(l-1)/2 - inv[i-l+1][i] + inv[1][i] - inv[1][i-l] - inv[i-l+1][i]);
// cout << i-l+1 << ' ' << i << ' ' << l*(l-1)/2 - inv[i-l+1][i] << ' ' << inv[1][i] - inv[1][i-l] - inv[i-l+1][i] << ' ' << dp[i-l] << '\n';
}
// cout << dp[i] << ' ';
}
cout << dp[N] << '\n';
}
