#include <cstdio>
#include <cmath>
const int M = 100005;
const int MOD = 1e9+7;
#define int long long
int read()
{
	int x=0,f=1;char c;
	while((c=getchar())<'0' || c>'9') {if(c=='-') f=-1;}
	while(c>='0' && c<='9') {x=(x<<3)+(x<<1)+(c^48);c=getchar();}
	return x*f;
}
int n,m,k,dp[500][M],fac[2*M],inv[2*M],ans;
void init(int n)
{
	fac[0]=inv[0]=inv[1]=1;
	for(int i=1;i<=n;i++) fac[i]=fac[i-1]*i%MOD;
	for(int i=2;i<=n;i++) inv[i]=inv[MOD%i]*(MOD-MOD/i)%MOD;
	for(int i=2;i<=n;i++) inv[i]=inv[i-1]*inv[i]%MOD;	
}
int C(int n,int m)
{
	if(n<m || m<0) return 0;
	return fac[n]*inv[m]%MOD*inv[n-m]%MOD;
}
int cal(int x)
{
	return C(x+n-1,n-1);
}
signed main()
{
	//freopen("perm.in","r",stdin);
	//freopen("perm.out","w",stdout);
	n=read();k=read();init(2e5);
	dp[0][0]=1;m=499;
	for(int i=1;i<=m;i++)
	{
		for(int j=i;j<=k;j++)
		{
			dp[i][j]=(dp[i-1][j-i]+dp[i][j-i])%MOD;
			if(j>=n+1) dp[i][j]=(dp[i][j]-dp[i-1][j-n-1])%MOD; 
		} 
	}
	for(int i=0;i<=m;i++)
		for(int j=0;j<=k;j++)
		{
			int f=(i%2?-1:1);
			ans=(ans+1ll*f*dp[i][k-j]*cal(j))%MOD;
		}
	printf("%lld\n",(ans+MOD)%MOD);
}