#include <bits/stdc++.h>
using namespace std;
const long long mod = 1e9 + 7;
const int MaxN = 5e3 + 5;
int n;
int arr[MaxN];
void Inp()
{
cin >> n;
for (int x = 1; x <= n; x++)
{
cin >> arr[x];
}
}
int rev[MaxN];
int Pre[MaxN][MaxN];
long long F[MaxN];
void Exc()
{
for (int x = 1; x <= n; x++)
{
rev[arr[x]] = x;
}
for (int x = 1; x <= n; x++)
{
for (int y = 1; y <= n; y++)
{
Pre[x][y] = Pre[x][y - 1] + (rev[y] < rev[x]);
}
}
F[n + 1] = 0;
for (int x = n; x > 0; x--)
{
F[x] = 1e18;
long long cur = 0;
for (int y = x; y <= n; y++)
{
cur += Pre[y][n] - Pre[y][x - 1];
cur -= (y - x) - (Pre[y][y] - Pre[y][x - 1]);
F[x] = min(F[x], F[y + 1] + cur);
}
}
cout << F[1];
}
int main()
{
//freopen("A.INP", "r", stdin);
//freopen("A.OUT", "w", stdout);
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
int test = 1;
//cin >> test;
for (int x = 1; x <= test; x++)
{
Inp();
Exc();
}
return 0;
}
