#include <bits/stdc++.h>
using namespace std;
const int maxn = 5005;
const int inf = 1e9;
int n;
int a[maxn], positions[maxn], toRem[maxn];
int dp[maxn];
struct FenwickTree
{
int tree[maxn];
void reset(int MAX)
{
fill(tree, tree + MAX + 1, 0);
}
void update(int pos, int val)
{
for (; pos <= n; pos += (pos & (-pos)))
{
tree[pos] += val;
}
}
int query(int pos)
{
int result = 0;
for (; pos >= 1; pos -= (pos & (-pos)))
{
result += tree[pos];
}
return result;
}
};
FenwickTree treeActive;
FenwickTree treeSmaller;
void fastIO()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
}
int main()
{
fastIO();
cin >> n;
for (int i = 1; i <= n; ++i)
{
cin >> a[i];
positions[a[i]] = i;
}
dp[n + 1] = 0;
for (int num = n; num >= 1; --num)
{
dp[num] = inf;
treeActive.update(positions[num], +1);
treeSmaller.reset(n);
int cost = 0;
for (int to = num; to <= n; ++to)
{
cost += treeActive.query(positions[to]) - 1;
treeSmaller.update(positions[to], +1);
cost -= treeSmaller.query(n) - treeSmaller.query(positions[to]);
dp[num] = min(dp[num], cost + dp[to + 1]);
}
}
cout << dp[1] << endl;
return 0;
}
