using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Text;

class TEST{
	static void Main(){
		Sol mySol =new Sol();
		mySol.Solve();
	}
}

class Sol{
	public void Solve(){
		
		Func<int, double> F = n =>{
			double a = 0;
			for(int i=1;i<=n;i++) a += Math.Pow(0.81,i);
			a = Math.Sqrt(a);
			double b = 0;
			for(int i=1;i<=n;i++) b += Math.Pow(0.9,i);
			return a / b;
		};
		
		var FInf = F(100000);
		
		Func<int, double> f = n => {
			double a = F(n) - FInf;
			double b = F(1) - FInf;
			return a / b * 1200;
		};
		
		Func<double, double> g = x =>{
			return Math.Pow(2,x/800.0);
		};
		
		Func<double, double> ginv = y =>{
			return Math.Log(y) / Math.Log(2) * 800;
		};
		
		double aa = 0;
		for(int i=1;i<=N;i++) aa += g(Pf[i-1]) * Math.Pow(0.9, i);
		double bb = 0;
		for(int i=1;i<=N;i++) bb += Math.Pow(0.9,i);
		
		var ans = ginv(aa / bb) - f(N);
		Console.WriteLine((int)Math.Round(ans));
	}
	int N;
	int[] Pf;
	public Sol(){
		N = ri();
		Pf = new int[N];
		for(int i=0;i<N;i++) Pf[i] = ri();
	}

	static String rs(){return Console.ReadLine();}
	static int ri(){return int.Parse(Console.ReadLine());}
	static long rl(){return long.Parse(Console.ReadLine());}
	static double rd(){return double.Parse(Console.ReadLine());}
	static String[] rsa(char sep=' '){return Console.ReadLine().Split(sep);}
	static int[] ria(char sep=' '){return Array.ConvertAll(Console.ReadLine().Split(sep),e=>int.Parse(e));}
	static long[] rla(char sep=' '){return Array.ConvertAll(Console.ReadLine().Split(sep),e=>long.Parse(e));}
	static double[] rda(char sep=' '){return Array.ConvertAll(Console.ReadLine().Split(sep),e=>double.Parse(e));}
}