#include <algorithm>
#include <iostream>
#include <numeric>
#include <vector>
typedef long long llong;
const int MAXN = 5000 + 10;
const int INF = 1e9;
int dp[MAXN];
int treePos[MAXN];
int treeSmaller[MAXN];
int a[MAXN], n;
int pos[MAXN];
void update(int tree[], int pos, int value)
{
for (int i = pos ; i <= n ; i += i & (-i))
{
tree[i] += value;
}
}
int query(int tree[], int pos)
{
int sum = 0;
for (int i = pos ; i >= 1 ; i -= i & (-i))
{
sum += tree[i];
}
return sum;
}
void solve()
{
dp[n+1] = 0;
for (int from = n ; from >= 1 ; --from)
{
std::fill(treeSmaller + 1, treeSmaller + 1 + n, 0);
update(treePos, pos[from], 1);
dp[from] = INF;
int add = 0;
for (int next = from ; next <= n ; ++next)
{
update(treeSmaller, pos[next], 1);
add += query(treePos, pos[next]) - 1;
add -= query(treeSmaller, n) - query(treeSmaller, pos[next]);
dp[from] = std::min(dp[from], dp[next + 1] + add);
}
}
std::cout << dp[1] << '\n';
}
void read()
{
std::cin >> n;
for (int i = 1 ; i <= n ; ++i)
{
std::cin >> a[i];
pos[a[i]] = i;
}
}
void fastIO()
{
std::ios_base :: sync_with_stdio(0);
std::cout.tie(nullptr);
std::cin.tie(nullptr);
}
int main()
{
fastIO();
read();
solve();
return 0;
}
