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#include <vector>
#include <cmath>
using namespace std;
 
static const unsigned MODVAL = 1000000007;
struct mint
{
	unsigned val;
	mint():val(0){}
	mint(int      x):val(x%MODVAL) {}
	mint(unsigned x):val(x%MODVAL) {}
};
mint& operator+=(mint& x, mint y) { return x = x.val+y.val; }
 
class AlienAndSetDiv1 { public:
	int getNumber(int N, int K)
	{
		memo.assign((1<<K)*(N+1)*(N+1), -1);
		vector<int> A, B;
		return rec(N, K, A, B, 0);
	}
 
	vector<int> memo;
	int rec(size_t N, int K, vector<int>& A, vector<int>& B, int lastk)
	{
		if(A.size()==N && B.size()==N)
			return 1;
 
		auto key = (lastk*(N+1)+A.size())*(N+1)+B.size();
		if(memo[key] >= 0)
			return memo[key];
 
		int next = A.size()+B.size()+1, nextmask = (lastk &~ (1<<(K-1)))<<1;
		int ai = A.size(), bi = B.size();
 
		mint total = 0;
 
		A.push_back(next);
		if(A.size()<=N && (ai>=B.size() || abs(A[ai]-B[ai])>=K))
			total += rec(N, K, A, B, nextmask);
		A.pop_back();
		B.push_back(next);
		if(B.size()<=N && (bi>=A.size() || abs(A[bi]-B[bi])>=K))
			total += rec(N, K, A, B, nextmask|1);
		B.pop_back();
 
		return memo[key] = total.val;
	}
};
 

prog.cpp: In member function ‘int AlienAndSetDiv1::rec(std::size_t, int, std::vector<int>&, std::vector<int>&, int)’:
prog.cpp:39:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   if(A.size()<=N && (ai>=B.size() || abs(A[ai]-B[ai])>=K))
                                 ^
prog.cpp:43:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   if(B.size()<=N && (bi>=A.size() || abs(A[bi]-B[bi])>=K))
                                 ^
/usr/lib/gcc/i486-linux-gnu/4.8/../../../i386-linux-gnu/crt1.o: In function `_start':
(.text+0x18): undefined reference to `main'
collect2: error: ld returned 1 exit status

Standard output is empty