import java.util.*;
import java.io.*;
import java.text.*;
public class Main{
    //SOLUTION BEGIN
    void pre() throws Exception{}
    void solve(int TC) throws Exception{
        int h = ni(), w = ni();
        TreeSet<Integer>[] row = new TreeSet[h], col = new TreeSet[w];
        int[][][] mat = new int[4][h][w];
        for(int i = 0; i< 4; i++){
            for(int j = 0; j< h; j++)
                for(int k = 0; k< w; k++){
                    if((i&1)==1)mat[i][j][k] = (i/1)==1?w:h;
                    else mat[i][j][k] = -1;
                }
        }
        char[][] g = new char[h][w];
        for(int i = 0; i< h; i++)g[i] = n().toCharArray();
        for(int i = 0; i< h; i++){
            for(int j = 0; j< w; j++){
                if(g[i][j]=='#')mat[0][i][j] = j;
                else mat[0][i][j] = (j==0?-1:mat[0][i][j-1]);
            }
            for(int j = w-1; j>= 0; j--){
                if(g[i][j]=='#')mat[1][i][j] = j;
                else mat[1][i][j] = (j==w-1?w:mat[1][i][j+1]);
            }
        }
        for(int j = 0; j< w; j++){
            for(int i = 0; i< h; i++){
                if(g[i][j]=='#')mat[2][i][j] = i;
                else mat[2][i][j] = (i==0?-1:mat[2][i-1][j]);
            }
            for(int i = h-1; i>= 0; i--){
                if(g[i][j] == '#')mat[3][i][j] = i;
                else mat[3][i][j] = (i==h-1?h:mat[3][i+1][j]);
            }
        }
        int ans = 0;
        for(int i = 0; i< h; i++)
            for(int j = 0; j< w; j++)
                ans = Math.max(ans, mat[1][i][j]-mat[0][i][j]+mat[3][i][j]-mat[2][i][j]-3);
        pn(ans);
    }
    //SOLUTION END
    void hold(boolean b)throws Exception{if(!b)throw new Exception("Hold right there, Sparky!");}
    long mod = (long)1000000007, IINF = (long)1e18;
    final int INF = (int)1e9, MX = (int)2e5+5;
    DecimalFormat df = new DecimalFormat("0.00000000000");
    double PI = 3.141592653589793238462643383279502884197169399, eps = 1e-8;
    static boolean multipleTC = false, memory = false;
    FastReader in;PrintWriter out;
    void run() throws Exception{
        in = new FastReader();
        out = new PrintWriter(System.out);
        //Solution Credits: Taranpreet Singh
        int T = (multipleTC)?ni():1;
        pre();for(int t = 1; t<= T; t++)solve(t);
        out.flush();
        out.close();
    }
    public static void main(String[] args) throws Exception{
        if(memory)new Thread(null, new Runnable() {public void run(){try{new Main().run();}catch(Exception e){e.printStackTrace();}}}, "1", 1 << 28).start();
        else new Main().run();
    }
    long gcd(long a, long b){return (b==0)?a:gcd(b,a%b);}
    int gcd(int a, int b){return (b==0)?a:gcd(b,a%b);}
    int bit(long n){return (n==0)?0:(1+bit(n&(n-1)));}
    void p(Object o){out.print(o);}
    void pn(Object o){out.println(o);}
    void pni(Object o){out.println(o);out.flush();}
    String n()throws Exception{return in.next();}
    String nln()throws Exception{return in.nextLine();}
    int ni()throws Exception{return Integer.parseInt(in.next());}
    long nl()throws Exception{return Long.parseLong(in.next());}
    double nd()throws Exception{return Double.parseDouble(in.next());}

    class FastReader{
        BufferedReader br;
        StringTokenizer st;
        public FastReader(){
            br = new BufferedReader(new InputStreamReader(System.in));
        }

        public FastReader(String s) throws Exception{
            br = new BufferedReader(new FileReader(s));
        }

        String next() throws Exception{
            while (st == null || !st.hasMoreElements()){
                try{
                    st = new StringTokenizer(br.readLine());
                }catch (IOException  e){
                    throw new Exception(e.toString());
                }
            }
            return st.nextToken();
        }

        String nextLine() throws Exception{
            String str = "";
            try{   
                str = br.readLine();
            }catch (IOException e){
                throw new Exception(e.toString());
            }  
            return str;
        }
    }
}

Measured memory_bytes: 130800