#include<stdio.h>
#include<algorithm>
using namespace std;
int main()
{
    int t,y,ans,mem;
    char sign;
    while(scanf("%d%d",&t,&y),t + y)
    {
        int field[510][510] = {0};
        ans = 0;
        scanf("%c",&sign);
        for(int i = 0; i < t; i++)
        {
            for(int j = 0; j < y + 1; j++)
            {
                scanf("%c",&sign);
                if(sign == '*')field[j][i] = -1;
            }
        }//ok
        for(int i = 0; i < y; i++)
        {
            for(int j = 0; j < t; j++)
            {
                if(j == 0 && field[i][j] != -1)field[i][j] = 1;
                else if(field[i][j - 1] == -1)field[i][j] = 1;
                else if(field[i][j] == 0)field[i][j] = field[i][j - 1] + 1;
            }
        }
        /*for(int i = 0; i < y; i++)
        {
            for(int j = 0; j < t; j++)
            {
                printf("%3d",field[j][i]);
            }
            printf("\n");
        }*/
        for(int i = 0; i < t; i++)
        {
            for(int j = 0; j < y; j++)
            {
                mem = field[j][i];
                for(int k = 0; k < j + 1; k++)
                {
                    if(field[j - k][i] == -1)break;
                    if(mem > field[j - k][i])mem = field[j - k][i];
                    ans = max(ans,mem * (k + 1));
                }
            }
        }
        printf("%d\n",ans);
    }
    return 0;
}