B. Unmergetime limit per test1 secondmemory limit per test256 megabytesinputstandard inputoutputstandard outputLet a and b be two arrays of lengths n and m, respectively, with no elements in common. We can define a new array \mathrm{merge}(a,b) of length n+m recursively as follows:  If one of the arrays is empty, the result is the other array. That is, \mathrm{merge}(\emptyset,b)=b and \mathrm{merge}(a,\emptyset)=a. In particular, \mathrm{merge}(\emptyset,\emptyset)=\emptyset.  If both arrays are non-empty, and a_1<b_1, then \mathrm{merge}(a,b)=[a_1]+\mathrm{merge}([a_2,\ldots,a_n],b). That is, we delete the first element a_1 of a, merge the remaining arrays, then add a_1 to the beginning of the result.  If both arrays are non-empty, and a_1>b_1, then \mathrm{merge}(a,b)=[b_1]+\mathrm{merge}(a,[b_2,\ldots,b_m]). That is, we delete the first element b_1 of b, merge the remaining arrays, then add b_1 to the beginning of the result. This algorithm has the nice property that if a and b are sorted, then \mathrm{merge}(a,b) will also be sorted. For example, it is used as a subroutine in merge-sort. For this problem, however, we will consider the same procedure acting on non-sorted arrays as well. For example, if a=[3,1] and b=[2,4], then \mathrm{merge}(a,b)=[2,3,1,4].A permutation is an array consisting of n distinct integers from 1 to n in arbitrary order. For example, [2,3,1,5,4] is a permutation, but [1,2,2] is not a permutation (2 appears twice in the array) and [1,3,4] is also not a permutation (n=3 but there is 4 in the array).There is a permutation p of length 2n. Determine if there exist two arrays a and b, each of length n and with no elements in common, so that p=\mathrm{merge}(a,b).InputThe first line contains a single integer t (1\le t\le 1000)  — the number of test cases. Next 2t lines contain descriptions of test cases. The first line of each test case contains a single integer n (1\le n\le 2000).The second line of each test case contains 2n integers p_1,\ldots,p_{2n} (1\le p_i\le 2n). It is guaranteed that p is a permutation.It is guaranteed that the sum of n across all test cases does not exceed 2000.OutputFor each test case, output "YES" if there exist arrays a, b, each of length n and with no common elements, so that p=\mathrm{merge}(a,b). Otherwise, output "NO".ExampleInput
6
2
2 3 1 4
2
3 1 2 4
4
3 2 6 1 5 7 8 4
3
1 2 3 4 5 6
4
6 1 3 7 4 5 8 2
6
4 3 2 5 1 11 9 12 8 6 10 7
Output
YES
NO
YES
YES
NO
NO
NoteIn the first test case, [2,3,1,4]=\mathrm{merge}([3,1],[2,4]).In the second test case, we can show that [3,1,2,4] is not the merge of two arrays of length 2.In the third test case, [3,2,6,1,5,7,8,4]=\mathrm{merge}([3,2,8,4],[6,1,5,7]).In the fourth test case, [1,2,3,4,5,6]=\mathrm{merge}([1,3,6],[2,4,5]), for example.
6
2
2 3 1 4
2
3 1 2 4
4
3 2 6 1 5 7 8 4
3
1 2 3 4 5 6
4
6 1 3 7 4 5 8 2
6
4 3 2 5 1 11 9 12 8 6 10 7

YES NO YES YES NO NO 
['dp', '*1800']