use std::io::*;

const SP: u8 = b' ';
const LF: u8 = b'\n';

struct CharacterInput<'a> {
    locked_stdin: StdinLock<'a>,
    bytes_buffer: Vec<u8>,
}

impl<'a> CharacterInput<'a> {
    fn read(&mut self, delimiter: u8) -> &[u8] {
        self.bytes_buffer.clear();

        let len = self
            .locked_stdin
            .read_until(delimiter, &mut self.bytes_buffer)
            .unwrap();

        if len > 0 {
            let len = len - 1;
            if self.bytes_buffer[len] == delimiter {
                self.bytes_buffer.truncate(len);
            }
        }

        &self.bytes_buffer
    }

    fn scan_u(&mut self, delimiter: u8) -> u32 {
        self.read(delimiter)
            .into_iter()
            .fold(0, |accumulator, byte| {
                (byte - b'0') as u32 + accumulator * 10
            })
    }

    fn scan_u_vec(&mut self, n: usize, separator: u8, delimiter: u8) -> Vec<u32> {
        let mut vector = Vec::with_capacity(n as usize);
        for _i in 0..n - 1 {
            vector.push(self.scan_u(separator));
        }
        vector.push(self.scan_u(delimiter));
        vector
    }

    fn scan_u_pair(&mut self, separator: u8, delimiter: u8) -> (u32, u32) {
        (self.scan_u(separator), self.scan_u(delimiter))
    }

    fn scan_u_triple(&mut self, separator: u8, delimiter: u8) -> (u32, u32, u32) {
        (
            self.scan_u(separator),
            self.scan_u(separator),
            self.scan_u(delimiter),
        )
    }

    fn scan_s(&mut self, delimiter: u8) -> &str {
        unsafe { std::str::from_utf8_unchecked(self.read(delimiter)) }
    }
}

fn create_cin<'a>(input: StdinLock<'a>, buffer_capacity: usize) -> CharacterInput {
    CharacterInput {
        locked_stdin: input,
        bytes_buffer: Vec::with_capacity(buffer_capacity),
    }
}

struct CharacterOutput {
    string_buffer: String,
}

impl CharacterOutput {
    fn push_s(&mut self, s: &str) {
        self.string_buffer += s;
    }

    fn add_s(&mut self, s: &str, separator: char) {
        self.push_s(s);
        self.string_buffer.push(separator);
    }

    fn push<T: ToString>(&mut self, n: T) {
        self.push_s(&n.to_string());
    }

    fn add<T: ToString>(&mut self, n: T, separator: char) {
        self.push(n);
        self.string_buffer.push(separator);
    }

    fn add_from_iterator<T: ToString, I>(
        &mut self,
        iterator: &mut I,
        length: usize,
        separator: char,
        delimiter: char,
    ) where
        I: Iterator<Item = T>,
    {
        for element in iterator.by_ref().take(length - 1) {
            self.add(element, separator);
        }
        self.add(iterator.next().unwrap(), delimiter);
    }

    fn flush(&mut self) {
        let out = stdout();
        let mut out = out.lock();
        out.write_all(self.string_buffer.as_bytes()).unwrap();
        self.string_buffer.clear();
    }
}

fn create_cout(capacity: usize) -> CharacterOutput {
    CharacterOutput {
        string_buffer: String::with_capacity(capacity),
    }
}

// easy
fn println<T: std::string::ToString>(s: T) {
    println!("{}", s.to_string());
}

fn print_from_iterator<T: ToString, I>(
    iterator: &mut I,
    length: usize,
    separator: &str,
    buffer_capacity: usize
) where
    I: Iterator<Item = T>,
{
    println!(
        "{}",
        iterator
            .map(|e| e.to_string())
            .collect::<Vec<String>>()
            .join(separator),
    );
}

// ------------------------------------------------------------------------

fn main() {
    let cin = stdin();
    let cin = &mut create_cin(cin.lock(), 64);
    let cout = &mut create_cout(0);

    let h = cin.scan_u(SP) as usize;
    let w = cin.scan_u(LF) as usize;

    let mut table = vec!(0 as i32; w * h);

    for y in 0..h {
        let s = cin.scan_s(LF);
        for byte in s.bytes().enumerate() {
            if byte.1 == b'#' {
                table[y * w + byte.0] = -1;
            }
        }
    }

    for y in 0..h {
        let index_offset = y * w;
        let mut x = 0;
        while x < w {
            if table[index_offset + x] == 0 {
                let start_x = x;
                let mut temp_x = start_x;
                while temp_x < w && table[index_offset + temp_x] != -1 {
                    temp_x += 1;
                }
                let count = temp_x - start_x;

                for i in 0..count {
                    table[index_offset + x + i] += count as i32;
                }
                x += count + 1;
            } else {
                x += 1;
            }
        }
    }

    for x in 0..w {
        let mut y = 0;
        while y < h {
            let index = y * w + x;
            if table[index] != -1 {
                let start_y = y;
                let mut temp_y = start_y;
                let mut count = 0;
                while temp_y < h && table[index + count * w] != -1 {
                    temp_y += 1;
                    count += 1;
                }

                for i in 0..count {
                    table[index + i * w] += count as i32;
                }
                y += count + 1;
            } else {
                y += 1;
            }
        }
    }

    cout.add(table.into_iter().max().unwrap() - 1, '\n');

    cout.flush();
}


Measured memory_bytes: 20732