#include<iostream>

#include<cstdio>

#include<cstring>

#include<algorithm>

using namespace std;

int const maxn=;

int n,h[maxn],f[maxn],g[maxn],ans;

int main()

{

    while()

    {

        scanf("%d",&n);

        if(!n)return ;

        memset(f,,sizeof f);

        memset(g,,sizeof g);

        for(int i=;i<=n;i++)scanf("%d",&h[i]);

        f[n]=; g[n]=; ans=;//

        for(int i=n;i;i--)

            for(int j=i+;j<=n;j++)

            {

                if(h[j]>h[i])f[i]=max(f[i],g[j]+);

                else if(h[j]<h[i])g[i]=max(g[i],f[j]+);

                ans=max(ans,g[i]);

            }

        printf("%d\n",ans);

    }

}