#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define fi first
#define se second
#define p(x,y) pair<ll,ll>(x,y)
#define BIT(i,x) ((x>>i)&1)
#define MASK(x) (1<<x)
#define ld long double
#define __builtin_popcount __builtin_popcountll
#define pll pair<ll,ll>
template<class T1,class T2>
bool maximize(T1 &x,const T2 &y)
{
if(x<y)
{
x=y;
return 1;
}
return 0;
}
template<class T1,class T2>
bool minimize(T1 &x,const T2 &y)
{
if(x>y)
{
x=y;
return 1;
}
return 0;
}
void online()
{
std::ios_base::sync_with_stdio(0);
cin.tie(0);
#ifdef thuc
freopen("input.INP","r",stdin);
freopen("output.OUT","w",stdout);
#endif
}
const int N=5e3+10,M=1e9+7;
struct Node
{
ll l,r,vl;
}Tree[22*N];
ll cnt;
vector<ll> Head;
ll n,a[N],pos[N];
ll make(ll x,ll y,ll z)
{
Tree[++cnt].l=x;
Tree[cnt].r=y;
Tree[cnt].vl=z;
return cnt;
}
ll build(ll l,ll r)
{
if(l==r) return make(0,0,0);
return make(build(l,(l+r)/2),build((l+r)/2+1,r),0);
}
ll update(ll i,ll l,ll r,ll pos,ll vl)
{
if(r<pos||pos<l) return i;
if(l==r) return make(0,0,vl);
ll x=update(Tree[i].l,l,(l+r)/2,pos,vl);
ll y=update(Tree[i].r,(l+r)/2+1,r,pos,vl);
return make(x,y,Tree[x].vl+Tree[y].vl);
}
ll query(ll i,ll l,ll r,ll l1,ll r1)
{
if(r1<l||r<l1) return 0;
if(l1<=l&&r<=r1) return Tree[i].vl;
return query(Tree[i].l,l,(l+r)/2,l1,r1)+query(Tree[i].r,(l+r)/2+1,r,l1,r1);
}
ll query(ll l,ll r,ll l1,ll r1)
{
if(l>r) return 0;
return query(Head[r],1,n,l1,r1)-query(Head[l-1],1,n,l1,r1);
}
ll c[N][N],f[N];
int main()
{
online();
cin>>n;
Head.push_back(build(1,n));
for(int i=1;i<=n;i++)
{
cin>>a[i];
pos[a[i]]=i;
Head.push_back(update(Head.back(),1,n,a[i],1));
}
memset(f,0x3f,sizeof f);
f[0]=0;
for(int i=1;i<=n;i++)
{
for(int j=i;j<=n;j++)
{
c[i][j]=c[i][j-1];
c[i][j]+=query(1,pos[j]-1,i,n);
c[i][j]-=query(pos[j],n,i,j-1);
minimize(f[j],f[i-1]+c[i][j]);
}
}
cout<<f[n];
}
