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 Rust (1.15.1) (judge verdict: Accepted)

fn main() {

//    let s = String::from("101");
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).unwrap();

//    println!("{}",s);
    let mut ans = 0;
    if &s[0..1] == "1" {
        ans = ans + 1;
    }
    if &s[1..2] == "1" {
        ans = ans + 1;
    }
    if &s[2..3] == "1" {
        ans = ans + 1;
    }
    println!("{}", ans);
}