#include <cstdio>
#include <stack>
#include <algorithm>
using namespace std;
static const int MAX = 501;
struct Rectangle { int height, pos; };
int H, W;
int buffer[MAX][MAX];
int T[MAX][MAX];

void printT() {
    for (int i = 0; i < H; i++) {
        for (int j = 0; j < W; j++) printf("%d ", T[i][j]);
        printf("\n");
    }
}

int getLargestRectangleR(int idx, int size) {
    stack<Rectangle> S;
    int maxv = 0;
    T[idx][size] = 0;

    Rectangle rect, pre;
    for (int i = 0; i <= size; i++) {
        rect.height = T[idx][i];
        rect.pos = i;
        if ( S.empty() ) {
            S.push(rect);
        } else {
            if (S.top().height < rect.height) S.push(rect);
            else if (S.top().height > rect.height) {
                int target = i;
                while ( !S.empty() && S.top().height >= rect.height) {
                    pre = S.top(); S.pop();
                    int area = pre.height * (i - pre.pos);
                    maxv = max(maxv, area);
                    target = pre.pos;
                }
                rect.pos = target;
                S.push(rect);
            }
        }
    }
    return maxv;
}

int getLargestRectangle() {
    for (int j = 0; j < W; j++) {
        for (int i = 0; i < H; i++) {
            if (buffer[i][j]) T[i][j] = 0;
            else T[i][j] = (i > 0) ? T[i-1][j] + 1 : 1;
        }
    }
    //printT();
    int maxv = 0;
    for (int i = 0; i < H; i++) maxv = max(maxv, getLargestRectangleR(i, W));
    return maxv;
}


int main()
{
    char ch[501];
    for (; ;) {
        scanf("%d %d", &H, &W);
        if (H == 0 && W == 0) break;
        for (int i = 0; i < H; i++) {
            scanf("%s", ch);
            for (int j = 0; j < W; j++) {
                if (ch[j] == '.') buffer[i][j] = 0;
                else buffer[i][j] = 1;
            }
        }
        printf("%d\n", getLargestRectangle());
    }
    return 0;
}

