#include <iostream>
#include <algorithm>
using namespace std;

const int MAXH = 501;
const int MAXW = 501;
int H, W;
char G[MAXH][MAXW];
int h[MAXH][MAXW];

int main() {
  while(cin >> H >> W && (H|W)) {
    for(int i = 0; i < H; ++i) {
      for(int j = 0; j < W; ++j) {
        cin >> G[i][j];
      }
    }
    for(int i = 0; i < H; ++i) {
      for(int j = 0; j < W; ++j) {
        if(G[i][j] == '.') {
          if(j) h[i][j] = h[i][j-1] + 1;
          else  h[i][j] = 1;
        } else {
          h[i][j] = 0;
        }
      }
    }
    int res = 0;
    for(int j = 0; j < W; ++j) {
      for(int i = 0; i < H; ++i) {
        int s = 0;
        int mini = 1<<28;
        for(int p = i; p < H; ++p) {
          ++s;
          mini = min(mini, h[p][j]);
          res = max(res, s*mini);
        }
      }
    }
    cout << res << endl;
  }
  return 0;
}