#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
typedef vector<int> vei;
typedef vector<vei> vevei;
#define coa \
for (auto i : a) { \
cout << i << ' '; \
} \
cout << '\n';
#define cia \
for (auto& i : a) { \
cin >> a; \
}
#define cna \
int n; \
cin >> n; \
vector<int> a(n); \
for (int i = 0; i < n; i++) { \
cin >> a[i]; \
}
#define cnka \
int n, k; \
cin >> n >> k; \
vector<int> a(n); \
for (int i = 0; i < n; i++) { \
cin >> a[i]; \
}
#define cnab \
int n; \
cin >> n; \
vector<int> a(n); \
for (int i = 0; i < n; i++) { \
cin >> a[i]; \
} \
vector<int> b(n); \
for (int i = 0; i < n; i++) { \
cin >> b[i]; \
}
#define all(a) (a).begin(), (a).end()
#define sz(a) (int) a.size()
#define con cout << "No\n"
#define coe cout << "Yes\n";
#define str string
#define pb push_back
#define ff first
#define sc second
#define pii pair<ll, ll>
#define mxe max_element
#define mne min_element
#define stf shrink_to_fit
#define f(i, l, r) for (int i = (l); i < (r); i++)
#define double ld
#define int ll
int pereh[5001][5001], dp[5001][5001];
struct fenwick {
int n;
vector<int> t;
fenwick() = default;
fenwick(int n_) {
n = n_;
t.assign(n + 1, 0);
}
void clear() {
t.assign(n + 1, 0);
}
int sum(int x) {
int ans = 0;
for (int i = x; i >= 0; i = (i & (i + 1)) - 1) {
ans += t[i];
}
return ans;
}
void upd(int pos, int delta) {
for (int i = pos; i < n; i = i | (i + 1)) {
t[i] += delta;
}
}
};
signed main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
int n; cin >> n;
vector<int> a(n);
for (auto& u : a) cin >> u;
vector<int> pos(n + 1);
f(i, 0, n)pos[a[i]] = i;
fenwick fw(n), fw2(n);
f(i, 1, n + 1)fw.upd(i, 1);
f(i, 1, n + 1) {
fw2.clear();
for (int j = i; j <= n; j++) {
pereh[i][j] = pereh[i][j - 1] + fw.sum(pos[j]) + fw2.sum(pos[j]) - (j - i);
//cout << i << ' ' << j << ' ' << pereh[i][j] << '\n';
fw2.upd(pos[j] + 1, 1);
}
fw.upd(pos[i] + 1, -1);
}
vector<int> best_dp(n + 1, 1e18);
best_dp[0] = 0;
f(i, 1, n + 1) {
for (int j = 1; j <= i; j++) {
dp[i][j] = pereh[j][i] + best_dp[j - 1];
//cout << i << ' ' << j << ' ' << dp[i][j] << '\n';
best_dp[i] = min(best_dp[i], dp[i][j]);
}
}
cout << best_dp[n] << '\n';
return 0;
}
