use std::env::args;
use std::fs::File;
use std::io::BufRead;
use std::io::BufReader;

fn split_once<'a>(s: &'a str, sep: &str) -> (&'a str, &'a str) {
    let i = s.find(sep).unwrap();
    let left = &s[..i];
    let right = &s[i+sep.len()..];
    return (left, right);
}

fn encode(name: &str) -> u16 {
    // convert name to u16 because it can be copied easily
    if name == "start" {
        return 0;
    } else if name == "end" {
        return 1;
    } else {
        assert!(name.bytes().count() <= 3);
        let mut x: u16 = 0;
        if name.chars().next().unwrap().is_uppercase() {
            x |= 1;
        }
        for (i, b) in name.to_lowercase().bytes().enumerate() {
            // ord('a') = 97
            // 24 possible chars -> 5 bits
            x |= ((b as u16) - 96) << (i * 5 + 1);
        }
        return x;
    }
}

fn walk(pos: u16, edges: &Vec<(u16, u16)>, visited: &Vec<u16>) -> u32 {
    if pos == 1 {
        return 1;
    }

    let mut v = visited.clone();
    v.push(pos);

    let mut sum = 0;
    for (a, b) in edges {
        let other;
        if pos == *a {
            other = *b;
        } else if pos == *b {
            other = *a;
        } else {
            continue;
        }
        if other & 1 == 0 && visited.contains(&other) {
            continue;
        }
        sum += walk(other, edges, &v);
    }
    return sum;
}

fn main() {
    let path = args().nth(1).unwrap();
    let file = File::open(path).unwrap();

    let mut edges = vec![];

    for line in BufReader::new(file).lines() {
        let l = line.unwrap();
        let (left, right) = split_once(&l, "-");
        edges.push((encode(left), encode(right)));
    }

    let sum = walk(0, &edges, &vec![]);
    print!("{}\n", sum);
}