Problem:
Score : 100 points

Problem Statement

Given is a lowercase English letter C that is not z. Print the letter that follows C in alphabetical order.

Constraints

C is a lowercase English letter that is not z.

Input

Input is given from Standard Input in the following format:

C

Output

Print the letter that follows C in alphabetical order.

Sample Input 1

a

Sample Output 1

b

a is followed by b.

Sample Input 2

y

Sample Output 2

z

y is followed by z.

Solution in Rust (1.15.1) (judge verdict: Runtime Error)

#![allow(unused)]

//input
//use std::io::Read;

//collections
//use std::collections::BTreeMap;
//use std::collections::BTreeSet;
//use std::collections::HashMap;
//use std::collections::HashSet;

//入力マクロここから
//https://qiita.com/tanakh/items/0ba42c7ca36cd29d0ac8
macro_rules! input {
    (source = $s:expr, $($r:tt)*) => {
        let mut iter = $s.split_whitespace();
        let mut next = || { iter.next().unwrap() };
        input_inner!{next, $($r)*}
    };
    ($($r:tt)*) => {
        let stdin = std::io::stdin();
        let mut bytes = std::io::Read::bytes(std::io::BufReader::new(stdin.lock()));
        let mut next = move || -> String{
            bytes
                .by_ref()
                .map(|r|r.unwrap() as char)
                .skip_while(|c|c.is_whitespace())
                .take_while(|c|!c.is_whitespace())
                .collect()
        };
        input_inner!{next, $($r)*}
    };
}

macro_rules! input_inner {
    ($next:expr) => {};
    ($next:expr, ) => {};

    ($next:expr, $var:ident : $t:tt $($r:tt)*) => {
        let $var = read_value!($next, $t);
        input_inner!{$next $($r)*}
    };
}

macro_rules! read_value {
    ($next:expr, ( $($t:tt),* )) => {
        ( $(read_value!($next, $t)),* )
    };

    ($next:expr, [ $t:tt ; $len:expr ]) => {
        (0..$len).map(|_| read_value!($next, $t)).collect::<Vec<_>>()
    };

    ($next:expr, chars) => {
        read_value!($next, String).chars().collect::<Vec<char>>()
    };

    ($next:expr, usize1) => {
        read_value!($next, usize) - 1
    };

    ($next:expr, $t:ty) => {
        $next().parse::<$t>().expect("Parse error")
    };
}
//入力マクロここまで

fn main() {
    input! {
        n: usize,
        k: usize,
        m: usize,
        a: [usize;n-1],
    }

    let s: usize = a.iter().sum();
    for i in 0..k + 1 {
        if (s + i) / n >= m {
            println!("{}", i);
            return;
        }
    }
    println!("-1");
}