0
{18: 1, 20: 1}
{18: 2, 20: 1, 15: 1, 19: 1}
{18: 2, 20: 1, 15: 1, 19: 1, 11: 1, 13: 1}
{18: 2, 20: 1, 15: 1, 19: 1, 11: 2, 13: 2, 4: 1, 14: 1}
{18: 3, 20: 1, 15: 2, 19: 2, 11: 2, 13: 3, 4: 1, 14: 2, 12: 1}
3