#include <fstream>
using namespace std;
int n,sol[5005],l[5005],v[5005],i,j,min1,poz,max1;
int main()
{	
	freopen("subsir2.in","r",stdin);
	freopen("subsir2.out","w",stdout);
	scanf("%d",&n);
	
	
	for (i=1;i<=n;++i)
		scanf("%d",&v[i]);
	
	for (i=n;i>=1;--i)
	{
		min1=1<<30;
		max1=min1;
		for (j=i+1;j<=n;++j)
			if (v[j]>=v[i]&&v[j]<min1)
				{
					min1=v[j];
					if (sol[j]<=max1)
						max1=sol[j],poz=j;
			}
		if (min1==1<<30)
			sol[i]=1;
		else
				sol[i]=sol[poz]+1,l[i]=poz;
	}
	min1=sol[1],poz=1,j=v[1];
	for (i=2;i<=n;++i)
		if (v[i]<j)
		{
			j=v[i];
			if (sol[i]<=min1) 
				min1=sol[i],poz=i;
		}
	printf("%d ",min1);


return 0;
}