#include <iostream>
#include <vector>
using namespace std;
const int mod = 1e9+7;

int main(){
  int N, K;
  cin >> N >> K;
  vector<int> A(N);
  for(int i = 0; i < N; ++i) cin >> A[i];
  vector<int> dp(K+1,0);
  dp[0] = 1;
  for(int i = 0; i < N; ++i){
    vector<int> dp_(K+1,0);
    int s = 0;
    for(int j = 0; j <= K; ++j){
      s += dp[j], s %= mod;
      if(j > A[i]) s += mod - dp[j-A[i]-1], s %= mod;
      dp_[j] += s, dp_[j] %= mod;
    }
    dp = dp_;
  }
  cout << dp[K] << endl;
}
