import java.io.IOException;
import java.io.InputStream;
import java.util.*;
 
public class Main implements Runnable {
	
    public static void main(String[] args) {
    	new Thread(null, new Main(), "", 16 * 1024 * 1024).start();
    }
    
    public void run() {
        FastScanner sc = new FastScanner();
        
        int h = sc.nextInt();
        int w = sc.nextInt();
        
        int[][] yoko = new int[h][w];
        int[][] tate = new int[h][w];

        for(int i=0;i<h;i++){
        	char[] a = sc.next().toCharArray();
        	int len = 0;
        	int start = 0;
        	for(int j=0;j<=w;j++){
        		if(j==w ||a[j] == '#'){
        			for(int k=start;k<j;k++){
        				yoko[i][k] = len;
        			}
        			start = j+1;
        			len = 0;
        		}
        		else{
        			len += 1;
        		}
        	}
        }
        
        for(int j=0;j<w;j++){
    		int len = 0;
    		int start = 0;
        	for(int i=0;i<=h;i++){
        		if(i==h || yoko[i][j] == 0){
        			for(int k=start;k<i;k++){
        				tate[k][j] = len;
        			}
        			start = i+1;
        			len = 0;
        		}
        		else{
        			len += 1;
        		}
        	}
        }
        
        int ans = 0;
        
        for(int i=0;i<h;i++){
        	for(int j=0;j<w;j++){
        		ans = Math.max(tate[i][j]+yoko[i][j],ans);
        	}
        }
        
        System.out.println(ans-1);
    }
}

class FastScanner {
	private final InputStream in = System.in;
	private final byte[] buffer = new byte[1024];
	private int ptr = 0;
	private int buflen = 0;
	private boolean hasNextByte() {
		if (ptr < buflen) {
			return true;
		} else {
			ptr = 0;
			try {
				buflen = in.read(buffer);
			} catch (IOException e) {
				e.printStackTrace();
			}
			if (buflen <= 0) {
				return false;
			}
		}
		return true;
	}
	private int readByte() {
		if (hasNextByte())
			return buffer[ptr++];
		else
			return -1;
	}
	private static boolean isPrintableChar(int c) {
		return 33 <= c && c <= 126;
	}
	public boolean hasNext() {
		while (hasNextByte() && !isPrintableChar(buffer[ptr]))
			ptr++;
		return hasNextByte();
	}
	public String next() {
		if (!hasNext())
			throw new NoSuchElementException();
		StringBuilder sb = new StringBuilder();
		int b = readByte();
		while (isPrintableChar(b)) {
			sb.appendCodePoint(b);
			b = readByte();
		}
		return sb.toString();
	}
	public long nextLong() {
		if (!hasNext())
			throw new NoSuchElementException();
		long n = 0;
		boolean minus = false;
		int b = readByte();
		if (b == '-') {
			minus = true;
			b = readByte();
		}
		if (b < '0' || '9' < b) {
			throw new NumberFormatException();
		}
		while (true) {
			if ('0' <= b && b <= '9') {
				n *= 10;
				n += b - '0';
			} else if (b == -1 || !isPrintableChar(b)) {
				return minus ? -n : n;
			} else {
				throw new NumberFormatException();
			}
			b = readByte();
		}
	}
	public int nextInt() {
		long nl = nextLong();
		if (nl < Integer.MIN_VALUE || nl > Integer.MAX_VALUE)
			throw new NumberFormatException();
		return (int) nl;
	}
	public int[] nextIntArray(int n){
		int[] a = new int[n];
		for(int i=0;i<n;i++){
			a[i] = nextInt();
		}
		return a;
	}
	public Integer[] nextIntegerArray(int n){
		Integer[] a = new Integer[n];
		for(int i=0;i<n;i++){
			a[i] = nextInt();
		}
		return a;
	}
	public double nextDouble() {
		return Double.parseDouble(next());
	}
}

Measured memory_bytes: 98688