#include <bits/stdc++.h>
// Author: Kazuki_Will_Win_VOI_8703
#define fi first
#define se second
#define pii pair<int, int>
#define ll long long
using namespace std;
const int mn = 5e3 + 5, lg2 = 20, mbit = (1 << 20) + 1, mm = 5e3 + 5, inf = 1e9;
int n, a[mn], dp[mn], pos[mn], small[mn][mn], big[mn][mn], prebig[mn][mn], presmall[mn][mn];
void solve(){
cin >> n;
for(int i = 1; i <= n; i++){
cin >> a[i];
pos[a[i]] = i;
}
// Nx: Dãy kq là dãy có dạng [x, 1] -> [y, x + 1] -> [z, y + 1] -> ...
for(int i = 1; i <= n; i++){
for(int j = n; j >= 1; j--){
big[i][j] = big[i][j + 1] + (pos[j] < pos[i]);
prebig[i][j] = prebig[i - 1][j] + big[i][j];
}
for(int j = i - 1; j >= 1; j --){
small[i][j] = small[i][j + 1] + (pos[j] < pos[i]);
presmall[i][j] = presmall[i - 1][j] + small[i][j];
}
}
fill(dp, dp + mn, inf);
dp[0] = 0;
for(int i = 1; i <= n; i++){
for(int j = 1; j <= i; j++){
dp[i] = min(dp[i], dp[j - 1]
+ prebig[i][i + 1] - prebig[j - 1][i + 1]
+ presmall[i][j] - presmall[j - 1][j]);
}
}
cout << dp[n] << '\n';
}
signed main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
int t = 1;
// cin >> t;
while(t--){
solve();
}
}
