#include <bits/stdc++.h>
#define pb push_back
#define ff first
#define ss second
#define ll long long
#define N 5002
#define INF 1000000000
using namespace std;
int a[N],dp[N],pos[N];
int p[N][N],x[N][N];
int main(){
int n;
cin >> n;
for(int i=1;i<=n;i++){
cin >> a[i];
pos[a[i]]=i;
}
for(int i=1;i<=n;i++){
for(int j=n;j>=1;j--){
if(a[j]<=i){
x[i][j]=x[i][j+1]+1;
}
else x[i][j]=x[i][j+1];
}
}
for(int i=1;i<=n;i++){
for(int j=1;j<=(n-i+1);j++){
int pp=pos[i+j-1];
int u=x[i-1][pp];
p[i][j]=p[i][j-1]+pp+u-i-(x[i+j-1][pp+1]-x[i-1][pp]);
}
}
for(int i=1;i<=n;i++){
dp[i]=INF;
}
for(int i=1;i<=n;i++){
for(int j=0;j<i;j++){
dp[i]=min(dp[j]+p[j+1][i-j],dp[i]);
}
}
cout << dp[n];
}
