#include <bits/stdc++.h>
using namespace std;
//#define int long long
#define faster ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
#define FOR for(int i=1;i<=n;i++)
#define lim 5005
#define mid (start+end)/2
#define pb push_back
vector<int> buy[lim];
int n;
int dizi[lim],mp[lim];
int duz[lim][lim],ters[lim][lim];
int dp[lim];
int tree[4*lim];
inline int query(int node,int start,int end,int l,int r){
if(start>end || start>r || end<l)return 0;
if(start>=l && end<=r)return tree[node];
return query(node*2,start,mid,l,r)+query(node*2+1,mid+1,end,l,r);
}
inline void update(int node,int start,int end,int l,int r,int val){
if(start>end || start>r || end<l)return ;
if(start>=l && end<=r){
tree[node]+=val;
return ;
}
update(node*2,start,mid,l,r,val),update(node*2+1,mid+1,end,l,r,val);
tree[node]=tree[node*2]+tree[node*2+1];
}
inline void build(int node,int start,int end){
tree[node]=0;
if(start==end)return ;
build(node*2,start,mid),build(node*2+1,mid+1,end);
}
inline int f(int sira){
if(sira>n)return 0;
if(~dp[sira])return dp[sira];
int cev=INT_MAX;
for(int i=sira;i<=n;i++){
cev=min(cev,f(i+1)+duz[sira][i]);
cev=min(cev,f(i+1)+ters[sira][i]);
}
return dp[sira]=cev;
}
int main(){
faster
cin>>n;
FOR{
dp[i]=-1;
cin>>dizi[i];
mp[dizi[i]]=i;
}
FOR{
int tut=query(1,1,n,dizi[i],n);
for(int j=1;j<=dizi[i];j++){
duz[j][dizi[i]]+=tut;
}
update(1,1,n,dizi[i],dizi[i],1);
}
FOR{
for(int j=1;j<=n;j++){
duz[i][j]+=duz[i][j-1];
//cout<<duz[i][j]<<" ";
}
//cout<<'\n';
}
build(1,1,n);
FOR{
update(1,1,n,dizi[i],dizi[i],i-1);
}
FOR{
for(int j=1;j<i;j++){
if(dizi[j]>dizi[i]){
buy[dizi[i]].pb(dizi[j]);
update(1,1,n,dizi[j],dizi[j],-1);
}
}
}
FOR{
for(int j=1;j<=n;j++){
ters[i][j]=query(1,1,n,1,j);
}
update(1,1,n,i,i,-(mp[i]-1));
for(auto a:buy[i]){
update(1,1,n,a,a,1);
}
for(int j=mp[i];j<=n;j++){
if(dizi[j]>i){
update(1,1,n,dizi[j],dizi[j],-1);
buy[dizi[j]].pb(dizi[j]);
}
}
}
//~ FOR{
//~ for(int j=1;j<=n;j++)cout<<ters[i][j]<<" ";
//~ cout<<endl;
//~ }
cout<<f(1)<<'\n';
return 0;
}
