#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define int ll
#define pii pair<int,int>
#define X first
#define Y second
#define F(n) Fi(i,n)
#define Fi(i,n) Fl(i,0,n)
#define Fl(i,l,n) for(int i=l;i<n;i++)
#define all(x) x.begin(),x.end()
#define sz(x) ((int)x.size())
#define abs(x) ((x)>0?(x):-(x))
#define pb push_back
int n,tab[5005][5005],stab[5005][5005],a[5005],b[5005],dp[5005];
int qry(int l1,int r1,int l2,int r2){
//cout<<l1<<" "<<r1<<" "<<l2<<" "<<r2<<endl;
//cout<<stab[r1][r2]<<" "<<stab[r1][l2-1]<<" "<<stab[l1-1][r2]<<" "<<stab[l1-1][l2-1]<<endl;
return stab[r1][r2]-stab[r1][l2-1]-stab[l1-1][r2]+stab[l1-1][l2-1];
}
signed main(){
ios_base::sync_with_stdio(0);cin.tie(0);
cin>>n;
F(n)cin>>a[i],b[a[i]]=i;
int s=0;
memset(tab,0,sizeof(tab));
F(n)for(int j=i+1;j<n;j++){
if(b[i+1]<b[j+1])s++,tab[i+1][j+1]=0;
else tab[i+1][j+1]=1;
}
for(int i=0;i<=n;i++)stab[i][0]=stab[0][i]=0;
for(int i=1;i<=n;i++){
for(int j=1;j<=n;j++)stab[i][j]=tab[i][j]+stab[i-1][j]+stab[i][j-1]-stab[i-1][j-1];
}
/*F(n+1){
Fi(j,n+1)cout<<stab[i][j]<<" ";
cout<<endl;
}*/
dp[n]=s;
for(int i=n-1;i>=1;i--){
dp[i]=1e9;
for(int j=i+1;j<=n;j++){
int tt=qry(1,i,i+1,j);
dp[i]=min(dp[i],dp[j]-(i*(j-i))+tt*2);
}
}
/*int no=n;
for(int i=n-1;i>=1;i--){
int tt=qry(1,i,i+1,no);
cout<<tt<<" "<<(i*(no-i))-tt<<endl;
if(tt<(i*(no-i))-tt){
s-=((i*(no-i))-tt*2);
no=i;
}
cout<<s<<endl;
}*/
s=1e9;
F(n)s=min(dp[i+1],s);
cout<<s<<endl;
return 0;
}
/*
5 4
5 3
5 1
4 3
4 1
3 1
2 1
8 7
*/
