/* 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
3 3
..#
#..
...
---+/
/+---test
10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................
---+/

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

  auto M = new bool[][](H);
  foreach (ref m; M) {
    m = readln.chomp.map!(c => c == '.').array;
  }

  auto rem_wh = long.max;
  auto visited = new bool[][](H, W);
  void F(long x, long y, long l) {
    if (x < 0 || y < 0 || x >= W || y >= H) return;
    if (!M[y][x]) return;

    if (x == W-1 && y == H-1) {
      rem_wh.amin(l);
      visited[y][x] = true;
      return;
    }
    if (visited[y][x]) return;
    visited[y][x] = true;

    ++l;
    F(x-1, y, l);
    F(x+1, y, l);
    F(x, y-1, l);
    F(x, y+1, l);
  }
  F(0, 0, 1);

  if (visited[$-1][$-1]) {
    (M.map!(x => x.count(true)).sum - rem_wh).writeln;
  } else {
    "-1".writeln;
  }
}
