a['~~'],i,n,s,m=1e9+7,*p;main(j){*a=1;scanf("%d%d%d",&n,&s,&j);for(s-=~-n*n/2*j;i++<n;)for(p=a;p-a<s;p++[i]%=m)p[i]+=*p;i=!printf("%d",s<0?0:a[s]);}