#include <iostream>
using namespace std;
const int MAXN = 5e3+5, INF = 1e9;
int N, A, pos[MAXN], inv[MAXN][MAXN], mov[MAXN][MAXN], dp[MAXN];
int main() {
ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
cin >> N;
for (int i=1;i<=N;i++) {
cin >> A;
pos[A] = i;
}
for (int i=N;i>=1;i--) {
for (int j=i+1;j<=N;j++) {
inv[i][j] = inv[i][j-1]+inv[i+1][j]-inv[i+1][j-1]+(pos[i]<pos[j]);
}
}
for (int i=N;i>=1;i--) {
for (int j=N;j>i;j--) {
mov[i][j] = mov[i+1][j]+mov[i][j+1]-mov[i+1][j+1]+(pos[i]>pos[j]);
}
}
for (int i=1;i<=N;i++) {
dp[i] = INF;
for (int j=0;j<i;j++) {
dp[i] = min(dp[i],dp[j]+inv[j+1][i]+mov[j+1][i+1]);
}
}
cout << dp[N] << "\n";
}
