There are three dices whose faces have different numbers from one another faces. Therefore numbers from 1 to 18 are distributed on the all the faces of three dices.

Well, we prepare the following dices which have the configuration:

Dice A | Dice B | Dice C |
---|---|---|

1 | 2 | 5 |

10 | 3 | 6 |

11 | 4 | 7 |

12 | 15 | 8 |

13 | 16 | 9 |

14 | 17 | 18 |

Actually, the above dices have an intriguing feature as follows. If your friend choose the dice A, you can win by dice B with the probability 7/12. If your friend choose the dice B, you can win by dice C with the probability 7/12. If your friend choose the dice C, you can win by dice A with the probability 25/36.

Therefore, you can always earn the higher probability than your friend.