dz pps 4

# задача 3
n = int(input())
a = []
for i in range(n):
    a += [int(input())]
print(sum(a) / len(a))
# задача 4
n, m = (int(input()) for i in range(2))
a = []
for i in range(n):
    a += [int(input())]
print(a[m])
# задача 5
n = int(input())
a = []
s = 0
for i in range(n):
    a += [int(input())]
for j in range(0, len(a), 2):
    s += a[j]
print(s)