#!/usr/bin/env php
cost 4: 0.001s
cost 5: 0.002s
cost 6: 0.003s
cost 7: 0.006s
cost 8: 0.012s
cost 9: 0.025s
cost 10: 0.050s
cost 11: 0.098s
cost 12: 0.197s
cost 13: 0.393s <--- cool
cost 14: 0.790s