Solution: +-----+-----+-----+-----+-----+ | | | 3 | | | +-----+-----+-----+-----+ + | | 1 1 | 2 | | | + + + +-----+ + | | 0 | 1 | | | + +-----+-----+ + + | | 2 | 2 1 | | | +-----+ +-----+-----+ + | | | | | | | 3 | | | | | +-----+-----+ + +-----+