#include <cstdio>
using namespace std;

bool a[500][500];
int b[500][500];

int main() {
  int h, w, t, x;
  char c, buf[501];
  while (1) {
    scanf("%d %d\n", &h, &w);
    if (!h && !w) break;
    for (int i=0; i<h; i++) {
      fgets(buf, sizeof(buf), stdin);
      for (int j=0; j<w; j++) {
        a[i][j] = (buf[j]=='*');
      }
    }

    x = 0;
    for (int i=0; i<h; i++) {
      b[i][w-1] = (a[i][w-1] ? 0 : 1);
      if (b[i][w-1] > x) x = b[i][w-1];
      for (int j=w-2; j>=0; j--) {
        b[i][j] = (a[i][j] ? 0 : (b[i][j+1]+1));
        if (b[i][j] > x) x = b[i][j];
      }
    }

    for (int i=1; i<h; i++) {
      for (int j=0; j<h-i; j++) {
        for (int k=0; k<w; k++) {
          b[j][k] = ((b[j][k]<b[j+1][k]) ? b[j][k] : b[j+1][k]);
          t = b[j][k] * (i+1);
          if (t > x) x = t;
        }
      }
    }
    printf("%d\n", x);
  }

  return 0;
}