# include <bits/stdc++.h>

const int N=155,INF=0x3f3f3f3f,mod=1e9+7;

inline int read(void){
	int res,f=1;
	char c;
	while((c=getchar())<'0'||c>'9')
		if(c=='-') f=-1;
	res=c-48;
	while((c=getchar())>='0'&&c<='9')
		res=res*10+c-48;
	return res*f;
}

int n,m;

inline int adc(int a,int b){
	return (a+b>=mod)?(a+b-mod):(a+b);
}
inline int dec(int a,int b){
	return (a<b)?(a-b+mod):(a-b);
}
inline int mul(int a,int b){
	return 1ll*a*b%mod;
}
inline void add(int &a,int b){
	a=adc(a,b);
}
inline void del(int &a,int b){
	a=dec(a,b);
}

inline int qpow(int d,int p){
	int ans=1;
	while(p){
		if(p&1) ans=1ll*ans*d%mod;
		d=1ll*d*d%mod,p>>=1;
	}
	return ans;
}

int f[N][N*N][2];

int main(void){
	n=read(),m=read();
	f[0][0][0]=1;
	
	for(int i=0;i<n;++i){
		for(int j=0;j<=n*(n+1)/2;++j){
			for(int p=0;p<=1;++p){
				if(!f[i][j][p]) continue;
				for(int k=i+1;k<=n;++k){
					int w=(k-i)*(k-i-1)/2;
					if(i<m&&k>=m) w+=(k-i);
					if(!p) del(f[k][j+w][1],f[i][j][p]);
					del(f[k][j+w][p],f[i][j][p]);
				}
			}
		}
	}
	int ans=0;
	for(int j=0;j<n*(n+1)/2;++j){
		int w=1ll*n*(n+1)/2*qpow(n*(n+1)/2-j,mod-2)%mod*qpow(n-1,mod-2)%mod;
		add(ans,dec(mul(mul(w,n),f[n][j][0]),mul(w,f[n][j][1])));
	}
	printf("%d",ans);
	
	return 0;
}