1449. Ambiguous permutations

单点时限: 2.0 sec

内存限制: 256 MB

Some programming contest problems are really tricky: not only do they require a different output format from what you might have expected, but also the sample output does not show the difference. For an example, let us look at permutations.

A permutation of the integers 1 to n is an ordering of these integers. So the natural way to represent a permutation is to list the integers in this order. With n = 5, a permutation might look like 2, 3, 4, 5, 1.

However, there is another possibility of representing a permutation: You create a list of numbers where the i-th number is the position of the integer i in the permutation. Let us call this second possibility an inverse permutation. The inverse permutation for the sequence above is 5, 1, 2, 3, 4.

An ambiguous permutation is a permutation which cannot be distinguished from its inverse permutation. The permutation 1, 4, 3, 2 for example is ambiguous, because its inverse permutation is the same. To get rid of such annoying sample test cases, you have to write a program which detects if a given permutation is ambiguous or not.

输入格式

The input contains several test cases.

The first line of each test case contains an integer n (1 <= n <= 100000). Then a permutation of the integers 1 to n follows in the next line. There is exactly one space character between consecutive integers. You can assume that every integer between 1 and n appears exactly once in the permutation.

The last test case is followed by a zero.

输出格式

For each test case output whether the permutation is ambiguous or not. Adhere to the format shown in the sample output.

样例

Input
4
1 4 3 2
5
2 3 4 5 1
1
1
0
Output
ambiguous
not ambiguous
ambiguous
Hint
Huge input,scanf is recommended.

11 人解决,14 人已尝试。

12 份提交通过,共有 17 份提交。

4.8 EMB 奖励。

创建: 14 年,1 月前.

修改: 4 年前.

最后提交: 9 月,4 周前.

来源: Ulm Local 2005

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