using System;
using System.Collections.Generic;
namespace I_am_the_brown_coder{
    class Inonoa{
        static void Main(){
            string[] h_w = Console.ReadLine().Split();
            int h = int.Parse(h_w[0]);
            int w = int.Parse(h_w[1]);

            bool[,] s = new bool[h,w];
            for(int i=0;i<h;i++){
                char[] tmpc = Console.ReadLine().ToCharArray();
                for(int j=0;j<w;j++){
                    if(tmpc[j]=='#'){
                        s[i,j] = true;
                    }else{
                        s[i,j] = false;
                    }
                }
            }

            int[,,] a = new int[h,w,2];

            int tmp = 0;
            while(tmp<h){
                if(s[tmp,0]) break;
                tmp++;
            }
            a[0,0,1] = tmp;
            tmp = 0;
            while(tmp<w){
                if(s[0,tmp]) break;
                tmp++;
            }
            a[0,0,0] = tmp;



            for(int i=1;i<h;i++){
                if(s[i,0]){a[i,0,0] = 0;a[i,0,1] = 0; continue;}
                tmp = 0;
                while(tmp<w){
                    if(s[i,tmp])break;
                    tmp ++;
                }
                a[i,0,0] = tmp;
                if(!s[i-1,0]){a[i,0,1] = a[i-1,0,1];continue;}
                tmp = 0;
                while(tmp+i<h){
                    if(s[tmp+i,0])break;
                    tmp ++;
                }
                a[i,0,1] = tmp;
            }

            for(int i=1;i<w;i++){
                if(s[0,i]){a[0,i,0] = 0;a[0,i,1] = 0;continue;}
                
                tmp = 0;
                while(tmp<h){
                    if(s[tmp,i])break;
                    tmp ++;
                }
                a[0,i,1] = tmp;

                if(!s[0,i-1]){a[0,i,0] = a[0,i-1,0];continue;}
                tmp = 0;
                while(i+tmp<w){
                    if(s[0,i+tmp])break;
                    tmp ++;
                }
                a[0,i,0] = tmp;
            }


            for(int i=1;i<h;i++){
                for(int j=1;j<w;j++){
                    if(s[i,j]){
                        a[i,j,0] = 0;
                        a[i,j,1] = 0;
                    }else{
                        if(!s[i,j-1]){
                            a[i,j,0] = a[i,j-1,0];
                        }else{
                            tmp = 0;
                            while(j+tmp+1<w){
                                if(s[i,j+tmp+1]){
                                    break;
                                }
                                tmp ++;
                            }
                            a[i,j,0] = tmp+1;
                        }

                        if(!s[i-1,j]){
                            a[i,j,1] = a[i-1,j,1];
                        }else{
                            tmp = 0;
                            while(i+tmp+1<h){
                                if(s[i+tmp+1,j]){
                                    break;
                                }
                                tmp ++;
                            }
                            a[i,j,1] = tmp+1;
                        }
                    }
                }
            }

            int ans = 0;
            for(int i=0;i<h;i++){
                for(int j=0;j<w;j++){
                    if(a[i,j,0]+a[i,j,1]-1>ans) ans = a[i,j,0]+a[i,j,1]-1;
                }
            }
            Console.WriteLine(ans);
        }
    }
}

Measured memory_bytes: 52168