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

int main()
{
	ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);
	//freopen("?.in","r",stdin);
	//freopen("?.out","w",stdout);
	int n, money = 0, ans = 0;
	cin >> n;
	int s[n];
	for(int i=0;i<n;i++)cin>>s[i];
	for(int i=0;i<n-1;i++)
	{
		if (money < 50)
		{
			money += ((s[i+1]-s[i])*1);
		}
		while (money >= 8)
		{
			ans++;
			money -= 8;
		}
	}
	cout << ans;
	return 0;
}