line = gets.chomp!
abort "format error" unless line=~/^\d+$/
n = line.to_i
abort "1<=n<=100" unless 1<=n && n<=100

rperf = [nil]
n.times{
    line = gets.chomp!
    abort "format error" unless line=~/^\d+$/
    rperf << line.to_r
}
abort "EOF" unless !gets


# 誤差を気にしない雑な解答


def large_f(n)
    n=10000 if n == :inf
    Math.sqrt((0..n).reduce{|s,i| s+0.81**i}) / (0..n).reduce{|s,i| s+0.9**i}
end

def small_f(n)
    ((large_f(n)-large_f(:inf)) / (large_f(1)-large_f(:inf)))*1200
end

def g(x)
    2.0**(x/800.0)
end

def g_inv(y)
    800.0*Math.log2(y)
end

def rating(n, rperf)
    g_inv((0..n).reduce{|s,i| s+g(rperf[i])*(0.9**i)} / (0..n).reduce{|s,i| s+0.9**i}) - small_f(n)
end

p rating(n, rperf).round