import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.StringTokenizer;
import java.io.IOException;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.InputStream;

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

    static class DLamp {
        public void solve(int testNumber, InputReader in, PrintWriter out) {
            int h = in.nextInt();
            int w = in.nextInt();
            int row[][] = new int[h][w];
            int col[][] = new int[h][w];
            int inp[][] = new int[h][w];
            for (int i = 0; i < h; i++) {
                String x = in.next();
                for (int j = 0; j < w; j++) {
                    if (x.charAt(j) == '#') inp[i][j] = 1;
                }
            }
            int count = 0;
            for (int i = 0; i < h; i++) {
                for (int j = 0; j < w; j++) {
                    int st = j;
                    count = 0;
                    while (st < w && inp[i][st] == 0) {
                        st++;
                        count++;
                    }
                    int tt = j;
                    j = st;
                    int end = st;
                    for (int k = tt; k < end && k < w; k++) row[i][k] = count;
                }
            }
            long ans = 0;
            for (int i = 0; i < w; i++) {
                for (int j = 0; j < h; j++) {
                    int st = j;
                    count = 0;
                    while (st < h && inp[st][i] == 0) {
                        st++;
                        count++;
                    }
                    int tt = j;
                    j = st;
                    int end = st;
                    for (int k = tt; k < end && k < h; k++) {
                        row[k][i] += count;
                        ans = Math.max(ans, row[k][i]);
                    }
                }
            }
            out.println(ans - 1);
        }

    }

    static class InputReader {
        public BufferedReader reader;
        public StringTokenizer tokenizer;

        public InputReader(InputStream stream) {
            reader = new BufferedReader(new InputStreamReader(stream), 32768);
            tokenizer = null;
        }

        public String next() {
            while (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    tokenizer = new StringTokenizer(reader.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken();
        }

        public int nextInt() {
            return Integer.parseInt(next());
        }

    }
}



Measured memory_bytes: 91200