{11: 1, 18: 1}
12 18
{11: 2, 18: 1, 12: 2}
17 18
{11: 2, 18: 1, 12: 2, 15: 3, 17: 3}
{11: 3, 18: 1, 12: 3, 15: 4, 17: 4, 9: 2}
{11: 3, 18: 1, 12: 3, 15: 4, 17: 4, 9: 2, 13: 4}
4