#include<stdio.h>
#include<stdlib.h>

typedef unsigned int uint;

#define POS(i,j) ((i)*(k+1)+(j))

void run(void){
  const uint mod=1000000007;
  uint n,k;
  scanf("%d%d",&n,&k);
  uint *dp=(uint *)calloc((n+1)*(k+1),sizeof(uint));
  dp[POS(1,0)]=1;
  uint i,j;
  for(i=2;i<=n;i++){
    uint local=0;
    for(j=0;j<=k && j<=i-1;j++){
      local=(local+dp[POS(i-1,j)])%mod;
      dp[POS(i,j)]=local;
    }
    for(;j<=k;j++){
      local=(local+dp[POS(i-1,j)]-dp[POS(i-1,j-i)]+mod)%mod;
      dp[POS(i,j)]=local;
    }
  }
  int sum=0;
  for(i=0;i<=k;i++) sum=(sum+dp[POS(n,i)])%mod;
  printf("%d\n",sum);
}

int main(void){
  run();
  return 0;
}