s = 0
k = 0
a = 100
for i in range(a):
b = int(input())
if b == 0:
break
if 9<b<100:
s+=b
k+=1
if k == 0:
print("NO")
else:
c = s / k
print(c)
школа 1747
s = 0
k = 0
a = 100
for i in range(a):
b = int(input())
if b == 0:
break
if 9<b<100:
s+=b
k+=1
if k == 0:
print("NO")
else:
c = s / k
print(c)