Suppose a country only issued two types of coins to be used as currency: one 7 unit coin and one 11 unit coin. This would cause a dilemma since certain prices could
not be paid exactly, such as 13 units. What would be the highest price that could not be paid with any combination of the two coins? Could you find any rule to follow? *
Let a and b be integers satisfying a>1 and b>1. Such a "highest prize" exists if and only if a and b are relatively prime. In this case, it is ab-a-b. For example, when a=11 and b=7, we get ab-a-b=59; when a=5 and b=9, we get ab-a-b=31.
哈哈哈哈 O(∩_∩)O哈哈~ 好久不来了，不小心看了一眼自己主页，发现自动关联了自己以往发过的帖，点进这个看了一眼，笑个半死。。。敢情我当初还发过这么搞笑的东西啊，我自己完全不记得了 
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发表于 2013-1-29 06:54:17
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