#include <iostream>
#include <string.h>
using namespace std;

int main() {
	char c[501];
	int w,h,da[501],db[501],dc[501],mx,s,p,i;
	db[0]=-1;
	while(cin >> h >> w) {
		if (w+h==0) break;
		for (i=0;i<w;i++) da[i]=0;
		mx=0;
		for (h;h>0;h--) {
			cin >> c;
			p=0; 
			for (i=0;i<w;i++) dc[i]=db[i]=0;
			for (i=0;i<=w;i++) {
				if (c[i]=='.') da[i]++; else da[i]=0;
				if (da[i]>db[p]) { p++; db[p]=da[i]; dc[p]=1; continue;}
				s=1;
				while(da[i]<db[p]) {
					s+=dc[p]; 
					if (mx<db[p]*(s-1)) { mx=db[p]*(s-1); } 
					dc[p--]=0;
				}
				if (da[i]>db[p]) { p++; db[p]=da[i]; dc[p]=s; } else dc[p]+=s;
			}
		}
    cout << mx << endl;
	}
return 0;	
}