import java.util.*; import java.io.*; import java.math.*;
public class Main{
	//Don't have to see. start------------------------------------------
	static class InputIterator{
		ArrayList<String> inputLine = new ArrayList<String>(1024);
		int index = 0; int max; String read;
		InputIterator(){
			BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
			try{
				while((read = br.readLine()) != null){
					inputLine.add(read);
				}
			}catch(IOException e){}
			max = inputLine.size();
		}
		boolean hasNext(){return (index < max);}
		String next(){
			if(hasNext()){
				return inputLine.get(index++);
			}else{
				throw new IndexOutOfBoundsException("There is no more input");
			}
		}
	}
	static HashMap<Integer, String> CONVSTR = new HashMap<Integer, String>();
	static InputIterator ii = new InputIterator();//This class cannot be used in reactive problem.
	static PrintWriter out = new PrintWriter(System.out);
	static void flush(){out.flush();}
	static void myout(Object t){out.println(t);}
	static void myerr(Object t){System.err.print("debug:");System.err.println(t);}
	static String next(){return ii.next();}
	static boolean hasNext(){return ii.hasNext();}
	static int nextInt(){return Integer.parseInt(next());}
	static long nextLong(){return Long.parseLong(next());}
	static double nextDouble(){return Double.parseDouble(next());}
	static ArrayList<String> nextStrArray(){return myconv(next(), 8);}
	static ArrayList<String> nextCharArray(){return myconv(next(), 0);}
	static ArrayList<Integer> nextIntArray(){
		ArrayList<String> input = nextStrArray(); ArrayList<Integer> ret = new ArrayList<Integer>(input.size());
		for(int i = 0; i < input.size(); i++){
			ret.add(Integer.parseInt(input.get(i)));
		}
		return ret;
	}
	static ArrayList<Long> nextLongArray(){
		ArrayList<String> input = nextStrArray(); ArrayList<Long> ret = new ArrayList<Long>(input.size());
		for(int i = 0; i < input.size(); i++){
			ret.add(Long.parseLong(input.get(i)));
		}
		return ret;
	}
	static String myconv(Object list, int no){//only join
		String joinString = CONVSTR.get(no);
		if(list instanceof String[]){
			return String.join(joinString, (String[])list);
		}else if(list instanceof ArrayList){
			return String.join(joinString, (ArrayList)list);
		}else{
			throw new ClassCastException("Don't join");
		}
	}
	static ArrayList<String> myconv(String str, int no){//only split
		String splitString = CONVSTR.get(no);
		return new ArrayList<String>(Arrays.asList(str.split(splitString)));
	}
	public static void main(String[] args){
		CONVSTR.put(8, " "); CONVSTR.put(9, "\n"); CONVSTR.put(0, "");
		solve();flush();
	}
	//Don't have to see. end------------------------------------------
	static void solve(){//Here is the main function
	ArrayList<Integer> one = nextIntArray();
	int H = one.get(0);
	int W = one.get(1);
	String[][] list = new String[H][W];
	Node[][] xy = new Node[H][W];
	for(int i = 0; i < H; i++){
      	ArrayList<String> tmp = nextCharArray();
		for(var j = 0; j < W; j++){
          	list[i][j] = tmp.get(j);
          	int add = (list[i][j].equals(".")) ? 1 : 0;
          	xy[i][j] = new Node(add, add);
		}
	}
	for(int i = 0; i < H; i++){
		for(int j = 0; j < W; j++){
			if(i == 0 && j == 0){continue;}
			if(j != 0){
				if(xy[i][j].x != 0){
					xy[i][j].x += xy[i][j - 1].x;
				}
			}
			if(i != 0){
				if(xy[i][j].y != 0){
					xy[i][j].y += xy[i - 1][j].y;
				}
			}
		}
	}
	for(int i = H - 1; i >= 0; i--){
		for(int j = W - 1; j >= 0; j--){
			if(list[i][j].equals("#")){continue;}
			if(i - 1 != -1 && list[i - 1][j].equals(".")){
				xy[i - 1][j].y = xy[i][j].y;
			}
			if(j - 1 != -1 && list[i][j - 1].equals(".")){
				xy[i][j - 1].x = xy[i][j].x;
			}
		}
	}
	int max = 0;
	for(int i = 0; i < H; i++){
		for(int j = 0; j < W; j++){
			max = Math.max(max, xy[i][j].x + xy[i][j].y - 1);
		}
	}
	myout(max);
	}
	//Method addition frame start

static class Node{
  int x;
  int y;
  Node(int x, int y){
    this.x = x;
    this.y = y;
  }
}

	//Method addition frame end
}


Measured memory_bytes: 462688