CF1855A.Dalton the Teacher

传统题 时间 2000 ms 内存 256 MiB 3 尝试 1 已通过 1 标签

Dalton the Teacher

Dalton is the teacher of a class with nn students, numbered from 11 to nn. The classroom contains nn chairs, also numbered from 11 to nn. Initially student ii is seated on chair pip_i. It is guaranteed that p1,p2,,pnp_1,p_2,\dots, p_n is a permutation of length nn.

A student is happy if his/her number is different from the number of his/her chair. In order to make all of his students happy, Dalton can repeatedly perform the following operation: choose two distinct students and swap their chairs. What is the minimum number of moves required to make all the students happy? One can show that, under the constraints of this problem, it is possible to make all the students happy with a finite number of moves.

A permutation of length nn is an array consisting of nn distinct integers from 11 to nn in arbitrary order. For example, [2,3,1,5,4][2,3,1,5,4] is a permutation, but [1,2,2][1,2,2] is not a permutation (22 appears twice in the array), and [1,3,4][1,3,4] is also not a permutation (n=3n=3 but there is 44 in the array).

Input

Each test contains multiple test cases. The first line contains the number of test cases tt (1t10001 \le t \le 1000). The description of the test cases follows.

The first line contains a single integer nn (2n1052 \le n \le 10^5) — the number of students.

The second line contains nn integers p1,p2,,pnp_1, p_2, \ldots, p_n (1pin1 \le p_i \le n) — pip_i denotes the initial chair of student ii. It is guaranteed that pp is a permutation.

It is guaranteed that the sum of nn over all test cases does not exceed 10510^5.

Output

For each test case, output the minimum number of moves required.

Note

In the first test case, both students are already happy, so Dalton can perform 00 moves.

In the second test case, Dalton can swap the chairs of students 11 and 22 to get the array [2,1,3][2, 1, 3]. Then he can swap chairs of students 22 and 33 to get the array [2,3,1][2, 3, 1]. At this point all the students are happy, and he performed 22 moves. It is impossible to perform the task with fewer moves.

In the third test case, by swapping the chairs of students 11 and 22 and then swapping the chairs of students 44 and 55, Dalton gets the array [2,1,5,3,4][2, 1, 5, 3, 4] in 22 moves.

Samples

5
2
2 1
3
1 2 3
5
1 2 5 4 3
4
1 2 4 3
10
10 2 1 3 6 5 4 7 9 8
0
2
2
1
1

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