import java.io.IOException;
import java.io.InputStream;
import java.util.NoSuchElementException;

public class Main {

    public static void main(String[] args) {
        FastScanner sc = new FastScanner();
        final int h = (int) sc.nextLong();
        final int w = (int) sc.nextLong();

        final short[][] map = new short[h][w];

        for (int height = 0; height < h; height++) {
            int lastWall = -1;
            for (int width = 0; width <= w; width++) {
                if (sc.readByte() != '.') {
                    if (lastWall != width - 1) {
                        final int len = width - lastWall - 1;
                        for (int i = lastWall + 1; i < width; i++) {
                            map[height][i] = (short) len;
                        }
                    }
                    lastWall = width;
                }
            }
        }

        int max = 0;
        for (int width = 0; width < w; width++) {
            int lastWall = -1;
            for (int height = 0; height < h; height++) {
                final int c = map[height][width];

                if (c == 0) {
                    if (lastWall != height - 1) {
                        int len = height - lastWall - 1;
                        for (int i = lastWall + 1; i < height; i++) {
                            final int v = map[i][width] + len;
                            if (v > max) max = v;
                        }
                    }
                    lastWall = height;
                }
            }

            if (lastWall != h - 1) {
                final int len = h - lastWall - 1;
                for (int i = lastWall + 1; i < h; i++) {
                    final int v = map[i][width] + len;
                    if (v > max) max = v;
                }
            }
        }

        System.out.println(max - 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();
            }
            return buflen > 0;
        }
    }
    int readByte() { if (hasNextByte()) return buffer[ptr++]; else return -1;}
    private static boolean isPrintableChar(int c) { return 33 <= c && c <= 126;}
    private void skipUnprintable() { while(hasNextByte() && !isPrintableChar(buffer[ptr])) ptr++;}
    public boolean hasNext() { skipUnprintable(); return hasNextByte();}
    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();
        }
    }
}


Measured memory_bytes: 30824