Problema de CodeForces 200b
# codeforces problem 200B solution in python. hope you've tried enough
n = int(input())
p = list(map(int, input().split()))[:n]
x = 100 / n
percentage = 0
for i in p:
if i != 0:
percentage += x / (100 / i)
print('%.12f' %percentage)
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