#include <iostream>
using namespace std;

int main()
{
	int h, w;
	while( cin >> h >> w && !( h == 0 && w == 0 ) ){
		if( h == 0 || w == 0 ){
			cout << 0 << endl;
			continue;
		}

		int ww = w + 1;
		int hh = h + 1;

		int* map = new int[ hh * ww ]();
		char* input = new char[ ww ]();

		for( int i = 0; i < h; ++i ){
			cin >> input;
			int* ptrMap = &map[ ( i + 1 ) * ww - 2 ];
			char* ptrInput = &input[ ww - 2 ];
			for( int j = 0; j < w; ++j, --ptrMap, --ptrInput ){
				if( *ptrInput == '.' ){
					*ptrMap = *( ptrMap + 1 ) + 1;
				}
			}
		}

		int maxArea = 0;
		for( int i = 0; i < h; ++i ){
			for( int j = 0; j < w; ++j ){
				int col = w;
				for( int row = 1; map[ ( i + row - 1 ) * ww + j ] != 0; ++row ){
					col = min( col, map[ ( i + row - 1 ) * ww + j ] );
					maxArea = max( maxArea, col * row );
				}
			}
		}

		cout << maxArea << endl;

		delete[] input;
		delete[] map;
	}

	return 0;
}