use std::cmp::max;

#[allow(unused_macros)]
macro_rules! scan {
    () => {
        {
            let mut line: String = String::new();
            std::io::stdin().read_line(&mut line).unwrap();
            line.trim().to_string()
        }
    };
    (;;) => {
        {
            let mut line: String = String::new();
            std::io::stdin().read_line(&mut line).unwrap();
            line.trim().split_whitespace().map(|s| s.to_string()).collect::<Vec<String>>()
        }
    };
    (;;$n:expr) => {
        {
            (0..$n).map(|_| scan!()).collect::<Vec<_>>()
        }
    };
    ($t:ty) => {
        {
            let mut line: String = String::new();
            std::io::stdin().read_line(&mut line).unwrap();
            line.trim().parse::<$t>().unwrap()
        }
    };
    ($($t:ty),*) => {
        {
            let mut line: String = String::new();
            std::io::stdin().read_line(&mut line).unwrap();
            let mut iter = line.split_whitespace();
            (
                $(iter.next().unwrap().parse::<$t>().unwrap(),)*
            )
        }
    };
    ($t:ty;;) => {
        {
            let mut line: String = String::new();
            std::io::stdin().read_line(&mut line).unwrap();
            line.split_whitespace()
                .map(|t| t.parse::<$t>().unwrap())
                .collect::<Vec<_>>()
        }
    };
    ($t:ty;;$n:expr) => {
        (0..$n).map(|_| scan!($t;;)).collect::<Vec<_>>()
    };
    ($t:ty; $n:expr) => {
        (0..$n).map(|_|
                    scan!($t)
        ).collect::<Vec<_>>()
    };
    ($($t:ty),*; $n:expr) => {
        (0..$n).map(|_|
                    scan!($($t),*)
        ).collect::<Vec<_>>()
    };
}

fn main() {
    let (h, w) = scan!(usize, usize);
    let vs = scan!(String; h)
        .iter()
        .map(|v| v.chars().collect::<Vec<_>>())
        .collect::<Vec<_>>();
    let mut hs = vec![vec![0; w]; h];

    for i in 0..h {
        let mut n = 0;
        for j in 0..w {
            if vs[i][j] == '#' {
                n = 0
            } else {
                n += 1
            }
            hs[i][j] = n
        }

        let mut n = 0;
        for j in 0..w {
            if hs[i][w - 1 - j] == 0 {
                n = 0
            } else if j == 0 {
                n = hs[i][w - 1 - j];
            } else if hs[i][w - j] == 0 && hs[i][w - 1 - j] != 0 {
                n = hs[i][w - 1 - j]
            }

            hs[i][w - 1 - j] = n;
        }
    }

    let mut ws = vec![vec![0; w]; h];
    for i in 0..w {
        let mut n = 0;
        for j in 0..h {
            if vs[j][i] == '#' {
                n = 0
            } else {
                n += 1
            }
            ws[j][i] = n
        }

        let mut n = 0;
        for j in 0..h {
            if ws[h - 1 - j][i] == 0 {
                n = 0
            } else if j == 0 {
                n = ws[h - 1 - j][i];
            } else if ws[h - j][i] == 0 && ws[h - 1 - j][i] != 0 {
                n = ws[h - 1 - j][i]
            }
            ws[h - 1 - j][i] = n;
        }
    }
    let mut ans = 0;
    for i in 0..h {
        for j in 0..w {
            ans = max(ans, hs[i][j] + ws[i][j])
        }
    }
    println!("{}", ans - 1);
}


Measured memory_bytes: 53472