#include <bits/stdc++.h>
using namespace std;
#define m_p make_pair
#define all(x) (x).begin(),(x).end()
#define sz(x) ((int)(x).size())
#define fi first
#define se second
typedef long long ll;
mt19937 rnd(chrono::steady_clock::now().time_since_epoch().count());
mt19937 rnf(2106);
const int N = 5003;
void por()
{
int n;
cin >> n;
vector<int> v;
for (int i = 1; i <= n; ++i)
v.push_back(i);
do
{
bool z = true;
for (int i = 0; i < n - 1; ++i)
{
if (v[i] >= v[i + 1] + 2)
{
z = false;
break;
}
}
if (z)
{
for (int i = 0; i < n; ++i)
cout << v[i] << ' ';
cout << "\n";
}
} while (next_permutation(all(v)));
}
int n;
int a[N];
int b[N];
int l[N][N], r[N][N];
int dp[N];
void solv()
{
cin >> n;
for (int i = 1; i <= n; ++i)
{
cin >> a[i];
}
for (int i = 1; i <= n; ++i)
{
memset(b, 0, sizeof b);
for (int j = 1; j < i; ++j)
b[a[j]]++;
for (int j = 1; j <= n; ++j)
l[a[i]][j] = l[a[i]][j - 1] + b[j];
memset(b, 0, sizeof b);
for (int j = i + 1; j <= n; ++j)
b[a[j]]++;
for (int j = 1; j <= n; ++j)
r[a[i]][j] = r[a[i]][j - 1] + b[j];
}
for (int x = 1; x <= n; ++x)
{
int s = l[x][n] - l[x][x];
dp[x] = dp[x - 1] + s;
for (int y = x - 1; y >= 1; --y)
{
s += l[y][n] - l[y][x];
s += r[y][x] - r[y][y];
dp[x] = min(dp[x], dp[y - 1] + s);
}
}
cout << dp[n] << "\n";
}
int main()
{
#ifdef SOMETHING
freopen("input.txt", "r", stdin);
//freopen("output.txt", "w", stdout);
#endif // SOMETHING
ios_base::sync_with_stdio(false), cin.tie(0);
int tt = 1;
//cin >> tt;
while (tt--)
{
solv();
}
return 0;
}
