a = int(input())
y = 0
for i in range(a):
b = list(map(int, input().split()))
score = 0
x = 0
for j in b[1:]:
score += j
for j in b[1:]:
if j > score/b[0]:
x += 1
y = x/b[0]*100
print("%.3f%%" %y)
YSA9IGludChpbnB1dCgpKQp5ID0gMApmb3IgaSBpbiByYW5nZShhKToKICAgIGIgPSBsaXN0KG1hcChpbnQsIGlucHV0KCkuc3BsaXQoKSkpCiAgICBzY29yZSA9IDAKICAgIHggPSAwCiAgICBmb3IgaiBpbiBiWzE6XToKICAgICAgICBzY29yZSArPSBqCiAgICBmb3IgaiBpbiBiWzE6XToKICAgICAgICBpZiBqID4gc2NvcmUvYlswXToKICAgICAgICAgICAgeCArPSAxCiAgICAgICAgICAgIHkgPSB4L2JbMF0qMTAwCiAgICBwcmludCgiJS4zZiUlIiAleSk=