#include <bits/stdc++.h>
#define ff first
#define ss second
#define endl '\n'
using namespace std;
const long long INF = (long long) 1e18;
const int mod = (int) 1e9+7;
const int MAXN = (int) 5e3+5;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
ll n;
int a[MAXN];
int dp[MAXN];
int s[MAXN];
int arr[MAXN][MAXN], brr[MAXN][MAXN];
int main(){
ios_base::sync_with_stdio(false);
cin.tie(nullptr);cout.tie(nullptr);
#ifdef Local
freopen("C:/Users/Admin/Desktop/Yazilim/C/IO/int.txt","r",stdin);
freopen("C:/Users/Admin/Desktop/Yazilim/C/IO/out.txt","w",stdout);
#endif
cin>>n;
for(int i = 1; i <= n; i++){
cin>>a[i];
}
for(int i = 1; i <= n; i++){
dp[i] = mod;
for(int j = a[i]; j <= n; j++)
s[j]++;
for(int j = a[i]; j <= n; j++){
arr[a[i]][j] = s[n] - s[j];
brr[a[i]][j] = (j - a[i]) - (s[j] - s[a[i]]);
}
}
for(int i = 1; i <= n; i++){
int sum = 0;
for(int j = i; j >= 1; j--){
sum += arr[j][i] + brr[j][i];
dp[i] = min(dp[i], dp[j - 1] + sum);
}
}
cout<<dp[n]<<endl;
#ifdef Local
cout<<endl<<fixed<<setprecision(2)<<1000.0 * clock() / CLOCKS_PER_SEC<< " milliseconds ";
#endif
}
