Problem:
Score : 200 points

Problem Statement

You are given a string S. Each character of S is uppercase or lowercase English letter.
Determine if S satisfies all of the following conditions:

The initial character of S is an uppercase A.

There is exactly one occurrence of C between the third character from the beginning and the second to last character (inclusive).

All letters except the A and C mentioned above are lowercase.

Constraints

4 ≤ |S| ≤ 10 (|S| is the length of the string S.)

Each character of S is uppercase or lowercase English letter.

Input

Input is given from Standard Input in the following format:

S

Output

If S satisfies all of the conditions in the problem statement, print AC; otherwise, print WA.

Sample Input 1

AtCoder

Sample Output 1

AC

The first letter is A, the third letter is C and the remaining letters are all lowercase, so all the conditions are satisfied.

Sample Input 2

ACoder

Sample Output 2

WA

The second letter should not be C.

Sample Input 3

AcycliC

Sample Output 3

WA

The last letter should not be C, either.

Sample Input 4

AtCoCo

Sample Output 4

WA

There should not be two or more occurrences of C.

Sample Input 5

Atcoder

Sample Output 5

WA

The number of C should not be zero, either.

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

use std::io::*;
use std::str::FromStr;

pub 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")
}

fn main() {
    let s: Vec<char> = read::<String>().chars().collect();

    if s[0] != 'A' {
        println!("WA");
        return;
    }

    let res = find_index(&s, 'C');
    if res.0 != 1 {
        println!("WA");
        return;
    }

    if !check_lower_case(&s, res.1) {
        println!("WA");
        return;
    }
    println!("AC");
}

fn check_lower_case(s: &Vec<char>, skip: usize) -> bool {
    for i in 1..s.len() {
        if i == skip {
            continue;
        }
        if !s[i].is_lowercase() {
            return false;
        }
    }
    return true;
}

fn find_index(s: &Vec<char>, t: char) -> (usize, usize) {
    // cnt index
    let mut cnt = 0;
    let mut idx = 0;
    for i in 0..s.len() {
        if i < 2 || i == s.len() - 1 {
            continue;
        }
        if s[i] == t {
            idx = i;
            cnt += 1;
        }
    }

    return (cnt, idx);
}