import java.util.Arrays;
import java.util.LinkedList;
import java.util.Scanner;

public class Main {
	
	public static long MOD = 1000000007;
	
	public static double pow(double d, int p){
		if(p == 0){
			return 0;
		}else if(p == 1){
			return d;
		}else if(p % 2 == 1){
			return d * pow(d, p - 1);
		}else{
			final double ret = pow(d, p / 2);
			return ret * ret;
		}
	}
	
	public static double F(int n){
		double nom = 0, denom = 0;
		for(int i = 1; i <= n; i++){
			nom += pow(0.81, i);
			denom += pow(0.9, i);
		}
		return Math.sqrt(nom) / denom;
	}
	
	public static double f(int n){
		final double F_INF = 0.2294157338705619;
		final double nom = F(n) - F_INF;
		final double denom = F(1) - F_INF;
		return nom / denom * 1200;
	}
	
	public static double g(int perf){
		return Math.pow(2.0, perf / 800.0);
	}
	
	public static double g_inv(double x){
		return 800 * Math.log(x) / Math.log(2.0);
	}
	
	public static double rating(int n, int[] perfs){
		double nom = 0, denom = 0;
		for(int i = 1; i <= n; i++){
			nom += g(perfs[i - 1]) * pow(0.9, i);
			denom += pow(0.9, i);
		}
		
		return g_inv(nom / denom) - f(n);
	}
	
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		final int N = sc.nextInt();
		int[] perfs = new int[N];
		for(int i = 0; i < N; i++){
			perfs[i] = sc.nextInt();
		}
		
		System.out.printf("%.00f\n", rating(N, perfs));
		
		
	}
}