#include <bits/stdc++.h>
using namespace std;
const int maxn = 5005;
const int inf = 1e9;
int n;
int p[maxn];
int pos[maxn];
int dp[maxn];
int tree_original[maxn];
void update_original(int idx, int val)
{
for (int i = idx; i <= n; i += (i & (-i)))
{
tree_original[i] += val;
}
}
int query_original(int idx)
{
int result = 0;
for (int i = idx; i >= 1; i -= (i & (-i)))
{
result += tree_original[i];
}
return result;
}
int tree[maxn];
void reset_tree()
{
for (int i = 1; i <= n; ++i)
{
tree[i] = 0;
}
}
void update_tree(int idx, int val)
{
for (int i = idx; i <= n; i += (i & (-i)))
{
tree[i] += val;
}
}
int query_tree(int idx)
{
int result = 0;
for (int i = idx; i >= 1; i -= (i & (-i)))
{
result += tree[i];
}
return result;
}
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 >> p[i];
pos[p[i]] = i;
}
dp[n + 1] = 0;
for (int i = n; i >= 1; --i)
{
update_original(pos[i], +1);
reset_tree();
dp[i] = 1e9;
int cost = 0;
for (int j = i; j <= n; ++j)
{
cost += query_original(pos[j]) - 1;
update_tree(pos[j], +1);
cost -= (query_tree(n) - query_tree(pos[j]));
dp[i] = min(dp[i], dp[j + 1] + cost);
}
}
cout << dp[1] << endl;
return 0;
}
