use std::cmp;
use std::collections::BinaryHeap; // 優先度付きキュー
use std::collections::HashMap; // 連想配列
use std::collections::HashSet; // 連想配列 キーのみ
use std::collections::VecDeque; // キュー or スタック
use std::io::Read;
use std::usize::MAX;

macro_rules! input {(source = $s:expr, $($r:tt)*) => {let mut iter = $s.split_whitespace();let mut next = || { iter.next().unwrap() };input_inner!{next, $($r)*}};($($r:tt)*) => {let stdin = std::io::stdin();let mut bytes = std::io::Read::bytes(std::io::BufReader::new(stdin.lock()));let mut next = move || -> String{bytes.by_ref().map(|r|r.unwrap() as char).skip_while(|c|c.is_whitespace()).take_while(|c|!c.is_whitespace()).collect()};input_inner!{next, $($r)*}};}
macro_rules! input_inner {($next:expr) => {};($next:expr, ) => {};($next:expr, $var:ident : $t:tt $($r:tt)*) => {let $var = read_value!($next, $t);input_inner!{$next $($r)*}};}
macro_rules! read_value {($next:expr, ( $($t:tt),* )) => {( $(read_value!($next, $t)),* )};($next:expr, [ $t:tt ; $len:expr ]) => {(0..$len).map(|_| read_value!($next, $t)).collect::<Vec<_>>()};($next:expr, chars) => {read_value!($next, String).chars().collect::<Vec<char>>()};($next:expr, usize1) => {read_value!($next, usize) - 1};($next:expr, [ $t:tt ]) => {{let len = read_value!($next, usize);(0..len).map(|_| read_value!($next, $t)).collect::<Vec<_>>()}};($next:expr, $t:ty) => {$next().parse::<$t>().expect("Parse error")};}

fn solve() {
    input! {
        h: usize,
        w: usize,
        board: [chars; h],
    }

    let mut board = board;

    let mut left = vec![vec![0; w]; h];
    let mut right = vec![vec![0; w]; h];
    let mut up = vec![vec![0; w]; h];
    let mut down = vec![vec![0; w]; h];

    // left
    for y in 0..h {
        let mut shine = 0;
        for x in 0..w {
            if board[y][x] == '.' {
                shine += 1;
            } else {
                shine = 0;
            }
            left[y][x] = shine;
        }
    }

    // right
    for y in 0..h {
        let mut shine = 0;
        for x in (0..w).rev() {
            if board[y][x] == '.' {
                shine += 1;
            } else {
                shine = 0;
            }
            right[y][x] = shine;
        }
    }

    // up
    for x in 0..w {
        let mut shine = 0;
        for y in 0..h {
            if board[y][x] == '.' {
                shine += 1;
            } else {
                shine = 0;
            }
            up[y][x] = shine;
        }
    }

    // down
    for x in 0..w {
        let mut shine = 0;
        for y in (0..h).rev() {
            if board[y][x] == '.' {
                shine += 1;
            } else {
                shine = 0;
            }
            down[y][x] = shine;
        }
    }

    let mut ans = 0;
    for x in 0..w {
        for y in 0..h {
            ans = cmp::max(left[y][x] + right[y][x] + up[y][x] + down[y][x] - 3, ans);
        }
    }

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

fn main() {
    let thd = std::thread::Builder::new().stack_size(104_857_600);
    thd.spawn(|| solve()).unwrap().join().unwrap();

    /*
    // 入力を一括で読み込む場合
    let mut buf = String::new();
    std::io::stdin().read_to_string(&mut buf).unwrap();
    let mut input = buf.split_whitespace();

    // inputに対しnext()で読み込んでいく
    let q: usize = input.next().unwrap().parse().unwrap();
    */
}

const LARGE_PRIME: u64 = 1_000_000_007;

// @〜でsnippet


Measured memory_bytes: 90492