Problem:
Score : 100 points

Problem Statement

Snuke has a grid consisting of three squares numbered 1, 2 and 3.
In each square, either 0 or 1 is written. The number written in Square i is s_i.

Snuke will place a marble on each square that says 1.
Find the number of squares on which Snuke will place a marble.

Constraints

Each of s_1, s_2 and s_3 is either 1 or 0.

Input

Input is given from Standard Input in the following format:

s_{1}s_{2}s_{3}

Output

Print the answer.

Sample Input 1

101

Sample Output 1

2

A marble will be placed on Square 1 and 3.

Sample Input 2

000

Sample Output 2

0

No marble will be placed on any square.

Solution in Common Lisp (SBCL 1.1.14) (judge verdict: Accepted)

(defun count_one (str index)
  (if (<= (length str) index) 0
    (if (equal (elt str index) #\0) 
      (count_one str (+ index 1))
      (+ 1 (count_one str (+ index 1)))
      )))

(format t "~A~%" (count_one (read-line) 0))