#include<iostream>
#include<cstdio>
#include<algorithm>
#include<vector>
#include<queue>
#include<map>
#include<set>
#include<climits>
#include<stack>
using namespace std;

int main(){
	int H, W;
	while(cin >> H >> W, H || W){
		char fld[500][500];
		int sum[501][501] = {};

		for(int i = 0; i < H; i++){
			for(int j = 0; j < W; j++){
				cin >> fld[i][j];
				if(fld[i][j] == '.') sum[i][j] = max(1, sum[i][j] );
				else sum[i][j] = 0;
				sum[i+1][j] = sum[i][j]+1;
			}
		}

		int ans = 0;
		for(int i = 0; i < H; i++){
			for(int j = 0; j < W; j++){
				int mi = INT_MAX;
				for(int k = 0; j+k < W && fld[i][j+k] == '.'; k++){
					mi = min(mi, sum[i][j+k] );
					ans = max(ans, mi*(k+1) );
				}
			}
		}
		printf("%d\n", ans);
	}
	return 0;
}