for gridnum, grid := range b.grids {
		for row, line := range grid {
			for col, elem := range line {
				if elem == item {
					ret = append(ret, markData{gridnum, row, col})
					// XXX: we should jump to the next grid
				}

	for gridnum := range b.grids {
		if m, ok := b.findInGrid(gridnum, item); ok {
			ret = append(ret, m)
		}
	}
	return ret
}
func (b Bingo) findInGrid(gridnum int, item int) (markData, bool) {
	for row, line := range b.grids[gridnum] {
		for col, elem := range line {
			if elem == item {
				return markData{gridnum, row, col}, true

	}
	if len(ret) == 0 {
		panic("mark not found in any grid")

	return ret

	return markData{}, false