// Copyright 2022 Christian Ulrich
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.
//
// usage: ./part1 < input

pub mod common;

use common::Map;

fn main() -> Result<(), &'static str> {
    let map = Map::from_stdin()?;
    let mut result = usize::MAX;
    for pos in map.lowest_positions() {
        let neighbors = map.neighbors(pos).unwrap();
        if neighbors
            .iter()
            .any(|n| map.square_height(*n).unwrap() as char == 'b')
        {
            result = usize::min(result, map.shortest_path(Some(pos)).count());
        }
    }
    println!("{result}");
    Ok(())
}