#include <iostream>
#include <algorithm>
using namespace std;

int main( void ) {
    int H, W;
    char M[501][501];
    int L[501][501];

    while ( cin >> H >> W && H && W ) {
        int answer = 0;

        for ( int i = 0; i < H; i++ ) {
            for ( int j = 0; j < W; j++ ) {
                cin >> M[i][j];
            }
        }

        for ( int i = 0; i < H; i++ ) {
            for ( int j = 0; j < W; j++ ) {
                if ( M[i][j] == '*' ) continue;
                L[i][j] = 0;
                for ( int k = 0; j+k < W; k++ ) {
                    if ( M[i][j+k] == '*' ) break;
                    L[i][j]++;
                }
            }
        }

        for ( int i = 0; i < H; i++ ) {
            for ( int j = 0; j < W; j++ ) {
                if ( M[i][j] == '*' ) continue;
                int w = L[i][j];
                int h = 0;
                for ( int k = 0; i+k < H; k++ ) {
                    if ( M[i+k][j] == '*' ) break;
                    if ( L[i+k][j] < w ) break;
                    w = min( w, L[i+k][j] );
                    h++;
                    answer = max( answer, w*h );
                }
            }
        }

        cout << answer << endl;
    }
    return 0;
}