import math

def F(n):
    a = 0
    for i in range(1, n+1):
        a += 0.81**i
    b = 0
    for i in range(1, n+1):
        b += 0.9**i
    return a**0.5/b
Finf = 0.22941573387056197

def f(n):
    return (F(n)-Finf)/(F(1)-Finf)*1200

def g(X):
    return 2.0 ** (X/800)

def invg(Y):
    return 800 * math.log2(Y)

def solve():
    n = int(input())
    ratings = []
    for i in range(n):
        ratings.append(int(input()))
    
    a = 0
    for i in range(1, n+1):
        a += g(ratings[i-1]) * 0.9**i
    b = 0
    for i in range(1, n+1):
        b += 0.9**i
    
    r = invg(a/b) - f(n)
    print(round(r))

solve()