#[allow(unused_imports)]
use std::cmp::*;
#[allow(unused_imports)]
use std::collections::*;
#[allow(unused_imports)]
use std::io::{Write, BufWriter};
// https://qiita.com/tanakh/items/0ba42c7ca36cd29d0ac8
macro_rules! input {
    ($($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 down = vec![vec![0; w+2]; h+2];
    let mut up = vec![vec![0; w+2]; h+2];
    let mut right = vec![vec![0; w+2]; h+2];
    let mut left = vec![vec![0; w+2]; h+2];

    for i in 0..board.len() {
        let mut sum = 0;
        for j in 0..board[0].len() {
            if board[i][j]=='.' {
                sum += 1;
            } else{
                sum = 0;
            }
            right[i+1][j+1] = sum;               
        }
    }
    for i in 0..board.len() {
        let mut sum = 0;
        for j in (0..board[0].len()).rev() {
            if board[i][j]=='.' {
                sum += 1;
            } else{
                sum = 0;
            }
            left[i+1][j+1] = sum;                
        }
    }
    for j in 0..board[0].len() {
        let mut sum = 0;
        for i in 0..board.len() {
            if board[i][j]=='.' {
                sum += 1;
            } else{
                sum = 0;
            }
            down[i+1][j+1] = sum;               
        }
    }
    for j in 0..board[0].len() {
        let mut sum = 0;
        for i in (0..board.len()).rev() {
            if board[i][j]=='.' {
                sum += 1;
            } else{
                sum = 0;
            }
            up[i+1][j+1] = sum;            
        }
    }
    let mut ans = 0;
    for i in 0..board.len() {
        for j in 0..board[0].len() {
            let mut sum = right[i+1][j]+left[i+1][j+2]+down[i][j+1]+up[i+2][j+1];
            if board[i][j]=='.'{
                sum += 1;
            }
            else{
                continue;
            }
            ans = max(ans, sum);
            // println!("{},{},{},{}",right[i+1][j],left[i+1][j+2],down[i][j+1],up[i+2][j+1]);
        }
    }
    println!("{}", ans);
}

// rotate 90 degree in counterclockwise
fn rotate(board: &Vec<Vec<usize>>) -> Vec<Vec<usize>> {
    let h = board.len();
    let w = board[0].len();
    let mut res = vec![vec![0; h]; w];
    for i in 0..h {
        for j in 0..w {
            res[w-1-j][i] = board[i][j];
        }
    }
    res
}

fn main() {
    // In order to avoid potential stack overflow, spawn a new thread.
    let stack_size = 104_857_600; // 100 MB
    let thd = std::thread::Builder::new().stack_size(stack_size);
    thd.spawn(|| solve()).unwrap().join().unwrap();
}


Measured memory_bytes: 90492