# Arup Guha
# 12/11/2024
# Solution to UCF HS Online Div 2 Problem: The Ducks of Danger Island

# Get input and sort.
n = int(input())
perc = [int(x) for x in input().split()]
perc.sort()

# Initial values.
exp = 0
curP = 1

# Go through the ducks in order from best to worst.
for i in range(n):

    # Probability of drop.
    drop = perc[i]/100
    probLast = curP*drop
    if i == n-1:
        probLast = curP

    # Add this into expectation.
    exp += (i+1)*probLast

    # New probability of moving onto next item.
    curP = curP*(1-drop)

# Ta da
print(exp)