import java.util.Scanner;
import java.util.stream.IntStream;

public class Main{
	static IntStream REPS(int v){return IntStream.range(0,v);}
	static IntStream REPS(int l,int r){return IntStream.rangeClosed(l,r);}
	static IntStream INS(int n) {return REPS(n).map(i->getInt());}
	static Scanner s=new Scanner(System.in);
	static int getInt(){return Integer.parseInt(s.next());}

	static final double finf=0.22941573387056172;
	public static void main(String[]$){
		int n=getInt(),perf[]=INS(n).toArray();
		System.out.println(
				(int)(gin(
						REPS(1,n).mapToDouble(i->g(perf[i-1])*Math.pow(0.9,i))
						.sum()
						/REPS(1,n).mapToDouble(i->Math.pow(0.9,i)).sum()
						)
				-f(n))
				);
	}
	private static double F(int n){
		return Math.sqrt(REPS(1,n).mapToDouble(i->Math.pow(0.81,i)).sum())
		/REPS(1,n).mapToDouble(i->Math.pow(0.9,i)).sum();
	}
	private static double f(int n){
		return (F(n)-finf)/(F(1)-finf)*1200;
	}
	private static double g(double n){
		return Math.pow(2,n/800.0);
	}
	private static double gin(double n){
		return 800*Math.log10(n)/Math.log10(2);
	}
}