while True:
    H,W = map(int, raw_input().split(" "))
    if (H,W) == (0,0):
        break
    field = [raw_input() for _ in xrange(H)]
    space = [[0]*(W+1) for _ in xrange(H)]
    for x in xrange(W-1,-1,-1):
        for y in xrange(H):
            if field[y][x]==".":
                space[y][x] = space[y][x+1]+1 
    ans = 0
    for x in xrange(W):
        for y in (yy for yy in xrange(H) if field[y][x] == "."):
            for hh in xrange(y+1,H+1):
                ans = max(ans, min(s[x] for s in space[y:h])*(h-y))
    print ans