#include<iostream>
#include<algorithm>
#include<vector>
#include<stack>
#include<map>
#include<set>
#include<queue>
#include<cstdio>
#include<climits>
#include<cmath>
#include<cstring>
#include<string>
#include<sstream>
#include<numeric>
#include<cassert>

#define f first
#define s second
#define mp make_pair

#define REP(i,n) for(int i=0; i<(int)(n); i++)
#define rep(i,s,n) for(int i=(s); i<(int)(n); i++)
#define FOR(i,c) for(__typeof((c).begin()) i=(c).begin(); i!=(c).end(); i++)
#define ALL(c) (c).begin(), (c).end()
#define IN(x,s,g) ((x) >= (s) && (x) < (g))
#define ISIN(x,y,w,h) (IN((x),0,(w)) && IN((y),0,(h)))
#define print(x) printf("%d\n",x)

using namespace std;

typedef unsigned int uint;
typedef long long ll;

char buff[510][510];
int memo[510][510];
int w,h;

int main(){
  while(scanf("%d%d ",&h,&w), w+h){
    REP(i,h){
      int cnt = 0;
      fgets(buff[i],sizeof(buff[i]),stdin);
      for(int j=w-1; j>=0; j--){
        if(buff[i][j] == '.'){
          memo[i][j] = ++cnt;
        }else{
          memo[i][j] = cnt = 0;
        }
      }
    }

    int ans = 0;
    REP(i,h) REP(j,w){
      int ww = INT_MAX;
      int k = 0;
      while(i+k < h && buff[i][j] == '.'){
        ww = min(ww, memo[i+k][j]);
        ans = max(ans, (k+1) * ww);
        k++;
      }
    }

    print(ans);
  }
  return 0;
}