#include<iostream>

int H, W;
char rect[500][500];
int a[500][500];

int main()
{
	while( std::cin >> H >> W, H | W )
	{
		for( int i = 0; i != H; ++i )
			for( int j = 0; j != W; ++j )
				std::cin >> rect[i][j];

		for( int i = 0; i != H; ++i )
		{
			for( int j = 0; j != W; ++j )
			{
				int k = j, cnt = 0;

				while( k < W && rect[i][k++] == '.' )
					++cnt;

				a[i][j] = cnt;
			}
		}

		int ans = 0;
		for( int i = 0; i != H; ++i )
		{
			for( int j = 0; j != W; ++j )
			{
				int w = 501;

				for( int k = 0; i + k < H; ++k )
				{
					w = std::min( w, a[i+k][j] );
					ans = std::max( ans, ( k + 1 ) * w );
				}
			}
		}

		std::cout << ans << std::endl;
	}

	return 0;
}