Problem:
Score : 100 points

Problem Statement

Snuke prepared 6 problems for a upcoming programming contest.
For each of those problems, Rng judged whether it can be used in the contest or not.

You are given a string S of length 6.
If the i-th character of s is 1, it means that the i-th problem prepared by Snuke is accepted to be used; 0 means that the problem is not accepted.

How many problems prepared by Snuke are accepted to be used in the contest?

Constraints

The length of S is 6.

S consists of 0 and 1.

Inputs

Input is given from Standard Input in the following format:

S

Outputs

Print the number of problems prepared by Snuke that are accepted to be used in the contest.

Sample Input 1

111100

Sample Output 1

4

The first, second, third and fourth problems are accepted, for a total of four.

Sample Input 2

001001

Sample Output 2

2

Sample Input 3

000000

Sample Output 3

0

Solution in Rust (1.15.1) (judge verdict: Accepted)

use std::io::*;
use std::str::FromStr;
 
fn read<T: FromStr>() -> T {
    let stdin = stdin();
    let stdin = stdin.lock();
    let token: String = stdin
        .bytes()
        .map(|c| c.expect("failed to read char") as char) 
        .skip_while(|c| c.is_whitespace())
        .take_while(|c| !c.is_whitespace())
        .collect();
    token.parse().ok().expect("failed to parse token")
}
 
#[allow(non_snake_case, unused_variables)]
fn main() {
    let S: String = read();
    println!("{}", S.chars().filter(|&c| c=='1').count());
}