Description

Input

Output

Sample Input

Sample Output

HINT

Source

#include<iostream>
#include<cstdio>
#include<cmath>
#include<cstring>
#include<cstdlib>
#include<algorithm>
#define F(i,j,n) for(int i=j;i<=n;i++)
#define D(i,j,n) for(int i=j;i>=n;i--)
#define ll long long
using namespace std;
int n,m,all,cnt[520];
ll ans,f[10][100][520];
bool p[520],g[520][520];
inline int read()
{
	int x=0,f=1;char ch=getchar();
	while (ch<'0'||ch>'9'){if (ch=='-') f=-1;ch=getchar();}
	while (ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}
	return x*f;
}
inline bool check(int x,int y)
{
	return ((x&y)==0)&&((x&(y>>1))==0)&&((y&(x>>1))==0);
}
inline void pre()
{
	int s=0;
	F(i,0,all) if ((i&(i>>1))==0)
	{
		s=0;
		for(int x=i;x;x>>=1) s+=(x&1);
		cnt[i]=s;
		p[i]=true;
	}
	F(i,0,all) if (p[i]) F(j,0,all) if (p[j]) g[i][j]=check(i,j);
}
int main()
{
	n=read();m=read();
	all=(1<<n)-1;
	pre();
	F(i,0,all) if (p[i]) f[1][cnt[i]][i]=1;
	F(i,1,n-1) F(j,0,all) if (p[j]) F(k,0,all) if (p[k]&&g[j][k])
		F(l,cnt[j],m-cnt[k]) f[i+1][l+cnt[k]][k]+=f[i][l][j];
	F(i,0,all) ans+=f[n][m][i];
	printf("%lld\n",ans);
}