Problems

# Number by 3

# Number by 3

The sequence of real numbers `a`

, _{1}`a`

,..., _{2}`a`

is given. Find the sum and the number of positive elements which indexes are divisible by _{n}**3**.

#### Input

The number of elements **n** (**n** ≤ **100**) in a sequence is given in the first line. Next line contains **n** real numbers, each value does not exceed **100** by absolute value.

#### Output

Print in one line the number of required elements and their sum with **2** digits after the decimal point.

Input example #1

6 6 7.5 2.1 2.0 0 -3

Output example #1

1 2.10