Problem:
Score : 400 points

Problem Statement

Snuke has N strings. The i-th string is s_i.

Let us concatenate these strings into one string after arranging them in some order.
Find the maximum possible number of occurrences of AB in the resulting string.

Constraints

1 \leq N \leq 10^{4}

2 \leq |s_i| \leq 10

s_i consists of uppercase English letters.

Input

Input is given from Standard Input in the following format:

N
s_1
\vdots
s_N

Output

Print the answer.

Sample Input 1

3
ABCA
XBAZ
BAD

Sample Output 1

2

For example, if we concatenate ABCA, BAD and XBAZ in this order, the resulting string ABCABADXBAZ has two occurrences of AB.

Sample Input 2

9
BEWPVCRWH
ZZNQYIJX
BAVREA
PA
HJMYITEOX
BCJHMRMNK
BP
QVFABZ
PRGKSPUNA

Sample Output 2

4

Sample Input 3

7
RABYBBE
JOZ
BMHQUVA
BPA
ISU
MCMABAOBHZ
SZMEHMA

Sample Output 3

4

Solution in Rust (1.15.1) (judge verdict: Wrong Answer)

use std::collections::VecDeque;
use std::collections::HashSet;
fn solve() {
    let s = std::io::stdin();
    let mut sc = Scanner { stdin: s.lock() };
    let n: usize = sc.read();
    let mut result = 0;

    let mut b1 = 0;
    let mut b2 = 0;
    let mut a1 = 0;
    let mut a2 = 0;

    let mut used = HashSet::new();
    let mut b1s: VecDeque<usize> = VecDeque::new();
    let mut a2s: VecDeque<usize> = VecDeque::new();
    let ss: Vec<Vec<char>> = (0..n)
        .map(|i| {
            let s = sc.chars();
            for x in s.windows(2) {
                if x[0] == 'A' && x[1] == 'B' {
                    result += 1;
                }
            }

            let c1 = s[0];
            let c2 = *s.last().unwrap();

            //head
            let mut tmp_a1 = if c1 == 'A' { 1 } else { 0 };
            let mut tmp_a2 = if c2 == 'A' { 1 } else { 0 };
            let mut tmp_b1 = if c1 == 'B' { 1 } else { 0 };
            let mut tmp_b2 = if c2 == 'B' { 1 } else { 0 };

            //XXXA
            //BXXX
            if tmp_a2 > 0 {
                while let Some(p) = b1s.pop_front() {
                    if !used.contains(&p) {
                        tmp_a2 = 0;
                        used.insert(p);
                        result += 1;
                        break;
                    }
                }
            }
            //BXXXX
            //XXXXA
            if tmp_b1 > 0 {
                while let Some(p) = a2s.pop_front() {
                    if !used.contains(&p) {
                        tmp_b1 = 0;
                        used.insert(p);
                        result += 1;
                        break;
                    }
                }
            }
            if tmp_b1 > 0 {
                b1s.push_back(i);
            }
            if tmp_a2 > 0 {
                a2s.push_back(i);
            }
            s
        })
        .collect();

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

fn main() {
    std::thread::Builder::new()
        .stack_size(64 * 1024 * 1024) // 64MB
        .spawn(|| solve())
        .unwrap()
        .join()
        .unwrap();
}
pub mod utils {
    const DYX: [(isize, isize); 8] = [
        (0, 1),   //right
        (1, 0),   //down
        (0, -1),  //left
        (-1, 0),  //top
        (1, 1),   //down right
        (-1, 1),  //top right
        (1, -1),  //down left
        (-1, -1), //top left
    ];

    pub fn try_adj(y: usize, x: usize, dir: usize, h: usize, w: usize) -> Option<(usize, usize)> {
        let ny = y as isize + DYX[dir].0;
        let nx = x as isize + DYX[dir].1;
        if ny >= 0 && nx >= 0 {
            let ny = ny as usize;
            let nx = nx as usize;
            if ny < h && nx < w {
                Some((ny, nx))
            } else {
                None
            }
        } else {
            None
        }
    }
}

//snippet from kenkoooo
pub struct Scanner<R> {
    stdin: R,
}

impl<R: std::io::Read> Scanner<R> {
    pub fn read<T: std::str::FromStr>(&mut self) -> T {
        use std::io::Read;
        let buf = self
            .stdin
            .by_ref()
            .bytes()
            .map(|b| b.unwrap())
            .skip_while(|&b| b == b' ' || b == b'\n' || b == b'\r')
            .take_while(|&b| b != b' ' && b != b'\n' && b != b'\r')
            .collect::<Vec<_>>();
        unsafe { std::str::from_utf8_unchecked(&buf) }
            .parse()
            .ok()
            .expect("Parse error.")
    }
    pub fn read_line(&mut self) -> String {
        use std::io::Read;
        let buf = self
            .stdin
            .by_ref()
            .bytes()
            .map(|b| b.unwrap())
            .skip_while(|&b| b == b'\n' || b == b'\r')
            .take_while(|&b| b != b'\n' && b != b'\r')
            .collect::<Vec<_>>();
        unsafe { std::str::from_utf8_unchecked(&buf) }
            .parse()
            .ok()
            .expect("Parse error.")
    }
    pub fn vec<T: std::str::FromStr>(&mut self, n: usize) -> Vec<T> {
        (0..n).map(|_| self.read()).collect()
    }

    pub fn chars(&mut self) -> Vec<char> {
        self.read::<String>().chars().collect()
    }
}