#include <bits/stdc++.h>
using namespace std;

const int N=310;

int dp[N][N], a[N];
int n;

int solve (int n)
{
    if (n==1 || n==2) return 0;
    int ret=n;
    for (int i=1;i<=n;i++) scanf ("%d", &a[i]);
    for (int i=1;i<=n;i++) for (int j=1;j<=n;j++) dp[i][j]=n;

    for (int i=1;i<=n;i++)
    {
        for (int j=1;j<=n;j++)
        {
            if (i==j) continue;
            for (int k=1;k<i;k++)
            {
                if (k!=j && a[k]<a[i]) dp[i][j]=min(dp[i][j], dp[k][j]-1);
            }
            for (int k=1;k<j;k++)
            {
                if (k!=i && a[k]>a[j]) dp[i][j]=min(dp[i][j], dp[i][k]-1);
            }
            ret=min(ret, dp[i][j]);
        }
    }
    return ret-2;
}

int main()
{
    while (true)
    {
        scanf ("%d", &n);
        if (n==-1) return 0;
        printf ("%d\n", solve(n));
    }

    return 0;
}