import sequtils,strutils,math

proc g(f : float64): float64=
    return pow(2.0,f / 800)
proc gr(f : float64):float64=
    return 800 * log2(f)
var
    N = stdin.readline.parseInt
    F,F1,Finf : float64
    Fd : array[1001,float64]
    Fm = Fd
    f : float64
    gd : float64
    gm = gd
for i in 1..1000:
    Fd[i] = pow(0.81, i.float64)
    Fm[i] = pow(0.9, i.float64)
F = sqrt(sum(Fd[1..N])) / sum(Fm[1..N])
F1 = 1
Finf = sqrt(sum(Fd)) / sum(Fm)
f = (F - Finf) / (F1 - Finf) * 1200


for n in 1..N:
    var a = stdin.readline.parseInt
    gm += g(a.float64) * pow(0.9, n.float64)
    gd += pow(0.9,n.float64)

var G = gr(gm / gd) - f
echo round(G).int