#include<bits/stdc++.h>
using namespace std;
#define L long long
typedef array<char,9> S;

void p(S arr, int n) {
  for (int i = 0; i < n; i++) {
    cout << ((int)arr[i]+1);
  }
}

int getBestConnected(map<S,int>&curr, vector<vector<char>>&d, int currC) {
  int res = 0;
  for (auto e = curr.begin(); e != curr.end(); e++) {
    bool succ = true;
    int group = -1;
    int score = e->second;
    for (int j = 0; j < 9; j++) {
      if (e->first[j] != -1) {
        if (group == -1) group = e->first[j];
        if (group != e->first[j]) {
          succ = false;
          break;
        }
        if (d[currC][j] == '.' && d[currC+1][j] == '.') {
          score++;
        }
      }
    }
    if (succ) {
      // cout << score << ":\t";
      // p(e->first,9);
      // cout << '\n';
      res = max(res, score);
    }
  }
  return res;
}

int main() {
  ios_base::sync_with_stdio(0); cin.tie(0);
  int r, c;
  cin >> r >> c;
  bool rev = c > r;
  if (rev) {
    swap(c, r);
  }
  vector<vector<char>> d(r+1, vector<char>(c, '#'));
  if (rev) for (int i = 0; i < c; i++) for (int j = 0; j < r; j++) cin >> d[j][i];
  else for (int i = 0; i < r; i++) for (int j = 0; j < c; j++) cin >> d[i][j];

  map<S,int> curr;
  char blk = -1;
  curr[{{blk,blk,blk,blk,blk,blk,blk,blk,blk}}] = 0;
  int res = 0;
  int entrances = 2;
  for (int i = 0; i < r; i++) {
    // string currPath = "";
    for (int j = 0; j < c; j++) {
      char cv = d[i][j];
      if (cv == 'U' || cv == 'D') entrances--;
      // currPath += cv;
      // cout << '\n' << currPath << '\n';
      map<S,int> nextV;
      auto push = [&](S&ns, int v) {
        // cout << "\t"; p(ns, c); cout << " " << v << '\n';
        nextV[ns] = max(v, nextV[ns]);
      };
      for (auto e = curr.begin(); e != curr.end(); e++) {
        // p(e->first, c); cout << " =>\n";
        int score = e->second;
        if (cv == '.' || cv == 'U' || cv == 'D') {
          int newScore = score;
          S ns = e->first;
          if (ns[j] == blk && i > 0 && d[i-1][j] == '.' && cv == '.') {
            newScore++;
          }
          if (j>0) {
            if (ns[j-1] != blk) {
              if (ns[j] == blk) {
                ns[j] = ns[j-1];
              } else if (ns[j-1] != ns[j]) {
                int from = ns[j], to = ns[j-1];
                if (from < to) {
                  swap(from, to);
                }
                for (int k = 0; k < c; k++) {
                  if (ns[k] == from) ns[k] = to;
                }
              }
            } else if (d[i][j-1] == '.' && cv == '.') {
              newScore++;
            }
          }
          if (ns[j] == blk) {
            ns[j] = j;
          }
          push(ns, newScore);
        }
        if (cv == '.' || cv == '#') {
          S ns = e->first;
          int newScore = score;
          if (cv == '.') {
            newScore += (i > 0 && ns[j] != blk && d[i-1][j] == '.') + (j>0 && ns[j-1] != blk && d[i][j-1] == '.');
          }
          if (ns[j] != j) {
            ns[j] = blk;
            push(ns, newScore);
          } else {
            int rpl = -1;
            for (int k = j+1; k < 9; k++) {
              if (ns[k] == j) {
                if (rpl == -1) rpl = k;
                ns[k] = rpl;
              }
            }
            if (rpl != -1) {
              ns[j] = blk;
              push(ns, newScore);
            }
          }
        }
      }
      swap(curr, nextV);
    }
    if (!entrances) {
      // cout << "INCLUDED:\n";
      res = max(res, getBestConnected(curr, d, i));
    }
  }

  cout << res << '\n';
}

/*

4 4
..#U
..#D
..#.
....

3 2
.U
..
.D

6 1
.
.
U
D
.
.

*/