#include<bits/stdc++.h>
using namespace std;
int s,n,a[100001],k;
map<long long,bool>b;
int main()
{
	cin>>n;
	for(int i=1;i<=n;++i)
	{
		cin>>a[i];
		b[a[i]]=1;
	}
	for(int i=1;i<=a[n];++i)
	{
		if(s<50) s++;
		if(b[a[i]]==1)
		{
			k=k+s/8;
			s/=8;
		}
	}
	cout<<k;
}