0
{11: 1, 18: 1}
{11: 1, 18: 1, 12: 1}
{11: 1, 18: 1, 12: 1, 15: 1, 17: 1}
{11: 2, 18: 1, 12: 2, 15: 2, 17: 1, 9: 1}
{11: 2, 18: 1, 12: 2, 15: 2, 17: 1, 9: 1, 13: 1}
2