Problem:
Score : 200 points

Problem Statement

You are given a string S consisting of uppercase English letters. Find the length of the longest ACGT string that is a substring (see Notes) of S.

Here, a ACGT string is a string that contains no characters other than A, C, G and T.

Notes

A substring of a string T is a string obtained by removing zero or more characters from the beginning and the end of T.

For example, the substrings of ATCODER include TCO, AT, CODER, ATCODER and (the empty string), but not AC.

Constraints

S is a string of length between 1 and 10 (inclusive).

Each character in S is an uppercase English letter.

Input

Input is given from Standard Input in the following format:

S

Output

Print the length of the longest ACGT string that is a substring of S.

Sample Input 1

ATCODER

Sample Output 1

3

Among the ACGT strings that are substrings of ATCODER, the longest one is ATC.

Sample Input 2

HATAGAYA

Sample Output 2

5

Among the ACGT strings that are substrings of HATAGAYA, the longest one is ATAGA.

Sample Input 3

SHINJUKU

Sample Output 3

0

Among the ACGT strings that are substrings of SHINJUKU, the longest one is (the empty string).

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

#![allow(unused)]

use std::{cell, cmp, collections, fmt, ops};

use cell::{Cell, RefCell};
use cmp::Ordering;
use collections::{BTreeMap, BTreeSet, BinaryHeap, HashMap, HashSet, LinkedList, VecDeque};
use fmt::{Debug, Display};
use ops::{
    Add, AddAssign, Deref, DerefMut, Div, DivAssign, Mul, MulAssign, Neg, Not, Sub, SubAssign,
};

// https://qiita.com/tanakh/items/0ba42c7ca36cd29d0ac8
#[macro_export]
macro_rules! input {
    (src = $s:expr, $($r:tt)*) => {
        let mut iter = $s.split_whitespace();
        _input_inner!(iter, $($r)*)
    };
    ($($r:tt)*) => {
        let mut s = {
            use std::io::Read;
            let mut s = String::new();
            std::io::stdin().read_to_string(&mut s).unwrap();
            s
        };
        input!(src = s, $($r)*)
    };
}

#[macro_export]
macro_rules! inputln {
    ($($r:tt)*) => {
        let mut s = {
            use std::io::Read;
            let mut s = String::new();
            std::io::stdin().read_line(&mut s).unwrap();
            s
        };
        let mut iter = s.split_whitespace();
        _input_inner!(iter, $($r)*)
    };
}

#[macro_export]
macro_rules! _input_inner {
    ($iter:expr) => {};
    ($iter:expr, ) => {};

    ($iter:expr, $var:ident : $t:tt $($r:tt)*) => {
        let $var = _parse_value!($iter, $t);
        _input_inner!($iter $($r)*)
    };

    ($iter:expr, mut $var:ident : $t:tt $($r:tt)*) => {
        let mut $var = _parse_value!($iter, $t);
        _input_inner!($iter $($r)*)
    };
}

#[macro_export]
macro_rules! _parse_value {
    ($iter:expr, ( $($t:tt),* )) => {
        ( $(_parse_value!($iter, $t)),* )
    };

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

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

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

    ($iter:expr, $t:ty) => {
        $iter.next().expect("No item left").parse::<$t>().expect("Parse error")
    };
}

#[cfg(feature = "debug")]
#[macro_export]
macro_rules! d {
    ($val:expr) => {
        match $val {
            tmp => {
                eprintln!("[{}] {} = {:#?}", line!(), stringify!($val), &tmp);
                tmp
            }
        }
    };
}

#[cfg(not(feature = "debug"))]
#[macro_export]
macro_rules! d {
    ($val:expr) => {
        $val
    };
}

/// ```
/// # use lib::*;
/// assert_eq!(vmin!(0, 1), 0);
/// assert_eq!(vmin!(3, 2, 1), 1);
/// ```
#[macro_export]
macro_rules! vmin {
    ($x:expr, $y:expr) => { std::cmp::min($x, $y) };
    ($x:expr, $($args:expr),*) => { std::cmp::min($x, vmin!($($args),*)) };
}

/// ```
/// # use lib::*;
/// assert_eq!(vmax!(0, 1), 1);
/// assert_eq!(vmax!(3, 2, 1), 3);
/// ```
#[macro_export]
macro_rules! vmax {
    ($x:expr, $y:expr) => { std::cmp::max($x, $y) };
    ($x:expr, $($args:expr),*) => { std::cmp::max($x, vmax!($($args),*)) };
}

pub mod num {
    /// ```
    /// # use lib::*;
    /// assert_eq!(num::gcd(2, 5), 1);
    /// assert_eq!(num::gcd(4, 6), 2);
    /// ```
    pub fn gcd(a: u64, b: u64) -> u64 {
        if b == 0 {
            a
        } else {
            gcd(b, a % b)
        }
    }

    /// ```
    /// # use lib::*;
    /// assert_eq!(num::gcd_slice(&[3]), 3);
    /// assert_eq!(num::gcd_slice(&[2, 5]), 1);
    /// assert_eq!(num::gcd_slice(&[4, 6, 8]), 2);
    /// ```
    pub fn gcd_slice(a: &[u64]) -> u64 {
        a.iter().fold(a[0], |a, b| gcd(a, *b))
    }

    /// ```
    /// # use lib::*;
    /// assert_eq!(num::lcm(2, 5), 10);
    /// assert_eq!(num::lcm(4, 6), 12);
    /// ```
    pub fn lcm(a: u64, b: u64) -> u64 {
        a * b / gcd(a, b)
    }

    /// ```
    /// # use lib::*;
    /// assert_eq!(num::lcm_slice(&[3]), 3);
    /// assert_eq!(num::lcm_slice(&[2, 5]), 10);
    /// assert_eq!(num::lcm_slice(&[4, 6, 8]), 24);
    /// ```
    pub fn lcm_slice(a: &[u64]) -> u64 {
        a.iter().fold(a[0], |a, b| lcm(a, *b))
    }
}

pub mod bits {
    /// ```
    /// # use lib::*;
    /// assert!(!bits::is_high(0b0100, 0));
    /// assert!(bits::is_high(0b0100, 2));
    /// ```
    pub fn is_high(bits: u64, pos: usize) -> bool {
        bits & (1 << pos as u64) != 0
    }

    /// ```
    /// # use lib::*;
    /// assert_eq!(bits::len(0b1010), 4);
    /// assert_eq!(bits::len(0b1), 1);
    /// assert_eq!(bits::len(0b0), 0);
    /// ```
    pub fn len(bits: u64) -> usize {
        for b in 0..64 {
            if is_high(bits, 63 - b) {
                return (64 - b) as usize;
            }
        }

        return 0;
    }
}

#[derive(Clone, Debug)]
pub struct UnionFind {
    parent: Vec<usize>,
    size: Vec<usize>,
    depth: Vec<usize>,
}

/// ```
/// # use lib::*;
/// let mut uf = UnionFind::new(4);
/// assert_eq!(uf.size(0), 1);
/// assert_eq!(uf.find(0), 0);
///
/// uf.union(0, 1);
/// assert!(uf.same(0, 1));
/// assert!(uf.find(0) == 0 || uf.find(0) == 1);
/// assert_eq!(uf.size(0), 2);
///
/// uf.union(1, 2);
/// assert!(uf.same(0, 2));
/// assert!(uf.find(0) == 0 || uf.find(0) == 1); // not 2
/// assert_eq!(uf.size(0), 3);
/// ```
impl UnionFind {
    pub fn new(capacity: usize) -> Self {
        UnionFind {
            parent: (0..capacity).collect(),
            size: vec![1; capacity],
            depth: vec![0; capacity],
        }
    }

    pub fn size(&mut self, a: usize) -> usize {
        let p = self.find(a);
        self.size[p]
    }

    pub fn find(&mut self, a: usize) -> usize {
        if self.parent[a] == a {
            a
        } else {
            let p = self.parent[a];
            self.parent[a] = self.find(p);
            self.parent[a]
        }
    }

    pub fn same(&mut self, a: usize, b: usize) -> bool {
        self.find(a) == self.find(b)
    }

    pub fn union(&mut self, a: usize, b: usize) {
        let a = self.find(a);
        let b = self.find(b);
        if a == b {
            return;
        }

        if self.depth[a] < self.depth[b] {
            self.parent[a] = b;
            self.size[b] += self.size[a];
        } else {
            self.parent[b] = a;
            self.size[a] += self.size[b];

            if self.depth[a] == self.depth[b] {
                self.depth[a] += 1;
            }
        }
    }
}

fn main() {
    input!(s: String);

    let ans = (0..s.len())
        .map(|b| {
            (b..s.len())
                .map(|e| &s[b..(e + 1)])
                .filter(|s| {
                    s.chars()
                        .all(|c| c == 'A' || c == 'C' || c == 'G' || c == 'T')
                })
                .map(|s| s.len())
                .max()
                .unwrap_or(0)
        })
        .max()
        .unwrap();

    println!("{}", ans);
}

#[cfg(test)]
mod tests {
    #[allow(unused)]
    use super::*;

    #[test]
    fn test() {
        //
    }
}