#include <bits/stdc++.h>
using namespace std;
using i64 = long long;
#define rep(i,s,e) for(int (i) = (s);(i) <= (e);(i)++)

i64 dp[303][303 * 303];

i64 MOD = 1e9 + 7;

int main(){
  int N,K;
  cin >> N >> K;
  dp[0][0] = 1;
  rep(i,0,N - 1){
    int a;
    cin >> a;
  }

  rep(i,0,N - 1){
    i64 sum = 0;
    rep(j,0,K){
      sum = (sum + dp[i][j]) % MOD;
      dp[i + 1][j] = sum;
      if(j - i >= 0){
        sum = (sum - dp[i][j - i] + MOD) % MOD;
      }
    }
  }
  i64 ans = 0;
  rep(i,0,K){
    ans = (ans + dp[N][i]) % MOD;
  }
  cout << ans << endl;
}