/* imports all std modules {{{*/
import
  std.algorithm,
  std.array,
  std.ascii,
  std.base64,
  std.bigint,
  std.bitmanip,
  std.compiler,
  std.complex,
  std.concurrency,
  std.container,
  std.conv,
  std.csv,
  std.datetime,
  std.demangle,
  std.encoding,
  std.exception,
  std.file,
  std.format,
  std.functional,
  std.getopt,
  std.json,
  std.math,
  std.mathspecial,
  std.meta,
  std.mmfile,
  std.net.curl,
  std.net.isemail,
  std.numeric,
  std.parallelism,
  std.path,
  std.process,
  std.random,
  std.range,
  std.regex,
  std.signals,
  std.socket,
  std.stdint,
  std.stdio,
  std.string,
  std.system,
  std.traits,
  std.typecons,
  std.uni,
  std.uri,
  std.utf,
  std.uuid,
  std.variant,
  std.zip,
  std.zlib;
/*}}}*/

/* libnum {{{*/
void amax(N, Args...)(ref N x, Args y) {
  x = x.max(y);
}
void amin(N, Args...)(ref N x, Args y) {
  x = x.min(y);
}
auto maxE(R)(R r) if (isInputRange!R) {
  ElementType!R x = r.front;
  r.popFront();
  foreach (y; r) x.amax(y);
  return x;
}
auto minE(R)(R r) if (isInputRange!R) {
  ElementType!R x = r.front;
  r.popFront();
  foreach (y; r) x.amin(y);
  return x;
}
/*}}}*/

/+---test
4 6
#..#..
.....#
....#.
#.#...
---+/
/+---test
8 8
..#...#.
....#...
##......
..###..#
...#..#.
##....#.
#...#...
###.#..#
---+/

void main(string[] args) {
  long H, W;
  readf(" %d %d ", &H, &W);

  auto M = new bool[][](H);
  foreach (y; 0..H) {
    const s = readln.chomp;
    M[y] = s.map!(x => x == '#').array;
  }

  auto score = new long[][](H, W);
  foreach (y; 0..H) {
    long l;
    foreach (x; 0..W+1) {
      if (x == W || M[y][x]) {
        score[y][l..x] = x - l;
        l = x+1;
      }
    }
  }
  foreach (x; 0..W) {
    long t;
    foreach (y; 0..H+1) {
      if (y == H || M[y][x]) {
        foreach (i; t..y) score[i][x] += y - t - 1;
        t = y+1;
      }
    }
  }

  long ans;
  foreach (y; 0..H) foreach (x; 0..W) {
    ans.amax(score[y][x]);
  }
  ans.writeln;
}
