import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.io.BufferedWriter;
import java.io.Writer;
import java.io.OutputStreamWriter;
import java.util.InputMismatchException;
import java.io.IOException;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 *
 * @author Osmanys Alonso (osmanys@gmail.com)
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        OutputWriter out = new OutputWriter(outputStream);
        TaskD solver = new TaskD();
        solver.solve(1, in, out);
        out.close();
    }

    static class TaskD {
        public void solve(int testNumber, InputReader in, OutputWriter out) {
            int h = in.readInt();
            int w = in.readInt();
            boolean t[][] = new boolean[h][w];
            String line;
            for (int i = 0; i < h; i++) {
                line = in.readString();
                for (int j = 0; j < w; j++) {
                    if (line.charAt(j) == '#')
                        t[i][j] = true;
                }
            }
            int last;
            int up[][] = new int[h][w];
            for (int j = 0; j < w; j++) {
                last = -1;
                for (int i = 0; i < h; i++) {
                    if (t[i][j]) {
                        last = i;
                    }
                    up[i][j] = last;
                }
            }
            int down[][] = new int[h][w];
            for (int j = 0; j < w; j++) {
                last = h;
                for (int i = h - 1; i >= 0; i--) {
                    if (t[i][j]) {
                        last = i;
                    }
                    down[i][j] = last;
                }
            }
            int left[][] = new int[h][w];
            for (int i = 0; i < h; i++) {
                last = -1;
                for (int j = 0; j < w; j++) {
                    if (t[i][j]) {
                        last = j;
                    }
                    left[i][j] = last;
                }
            }
            int right[][] = new int[h][w];
            for (int i = 0; i < h; i++) {
                last = w;
                for (int j = w - 1; j >= 0; j--) {
                    if (t[i][j]) {
                        last = j;
                    }
                    right[i][j] = last;
                }
            }
            int c, max = 0;
            for (int i = 0; i < h; i++) {
                for (int j = 0; j < w; j++) {
                    c = (down[i][j] - up[i][j] - 1) + (right[i][j] - left[i][j] - 1) - 1;
                    if (c < 0)
                        c = 0;
                    if (max < c)
                        max = c;
                }
            }
            out.printLine(max);
        }

    }

    static class InputReader {
        private InputStream stream;
        private byte[] buf = new byte[1024];
        private int curChar;
        private int numChars;
        private InputReader.SpaceCharFilter filter;

        public InputReader(InputStream stream) {
            this.stream = stream;
        }

        public int read() {
            if (numChars == -1) {
                throw new InputMismatchException();
            }
            if (curChar >= numChars) {
                curChar = 0;
                try {
                    numChars = stream.read(buf);
                } catch (IOException e) {
                    throw new InputMismatchException();
                }
                if (numChars <= 0) {
                    return -1;
                }
            }
            return buf[curChar++];
        }

        public int readInt() {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
            }
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            int res = 0;
            do {
                if (c < '0' || c > '9') {
                    throw new InputMismatchException();
                }
                res *= 10;
                res += c - '0';
                c = read();
            } while (!isSpaceChar(c));
            return res * sgn;
        }

        public String readString() {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
            }
            StringBuilder res = new StringBuilder();
            do {
                if (Character.isValidCodePoint(c)) {
                    res.appendCodePoint(c);
                }
                c = read();
            } while (!isSpaceChar(c));
            return res.toString();
        }

        public boolean isSpaceChar(int c) {
            if (filter != null) {
                return filter.isSpaceChar(c);
            }
            return isWhitespace(c);
        }

        public static boolean isWhitespace(int c) {
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }

        public interface SpaceCharFilter {
            public boolean isSpaceChar(int ch);

        }

    }

    static class OutputWriter {
        private final PrintWriter writer;

        public OutputWriter(OutputStream outputStream) {
            writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));
        }

        public OutputWriter(Writer writer) {
            this.writer = new PrintWriter(writer);
        }

        public void close() {
            writer.close();
        }

        public void printLine(int i) {
            writer.println(i);
        }

    }
}



Measured memory_bytes: 139772