#include<iostream>
#include<vector>
#include<cassert>
using namespace std;

int main(){

  int n, k; cin>> n>> k;
  int a[n];
  for(int i=0; i<n; i++) cin>> a[i];

  const int mod=1e9+7;

  vector<vector<int>> dp(n+1, vector<int>(k+1, 0));
  for(int i=1; i<=n; i++) dp[i][0]=1;
  for(int i=2; i<=n; i++)for(int j=1; j<=k && j<=i*(i-1)/2; j++){
    (dp[i][j]+=dp[i-1][j])%=mod;
    (dp[i][j]+=dp[i][j-1])%=mod;
    if(j-i>=0){
      assert(dp[i][j]>=dp[i-1][j-1]);
      (dp[i][j]-=dp[i-1][j-i])%=mod;
    }
  }

  int ans=0;
  for(int j=0; j<=k; j++) (ans+=dp[n][j])%=mod;
  cout<< ans<< endl;  

  return 0;
}