#include <cassert>
#include <cmath>
#include <algorithm>
#include <iostream>
#include <iomanip>
#include <climits>
#include <map>
#include <queue>
#include <set>
#include <cstring>
#include <vector>

using namespace std;
typedef long long ll;

const ll MOD = 1000000007;

int main() {
  int N, K;
  cin >> N >> K;
  int A[N];
  for (int i = 0; i < N; ++i) {
    cin >> A[i];
  }

  int dp[N + 1][K + N + 1];
  memset(dp, 0, sizeof(dp));
  for (int k = 0; k <= K; ++k) {
    dp[0][k] = 1;
  }

  for (int i = 0; i < N; ++i) {
    for (int j = 0; j <= K; ++j) {
      if (j - i - 1 >= 0) {
        dp[i + 1][j] += (dp[i][j] - dp[i][j - i - 1] + MOD);
        dp[i + 1][j] %= MOD;
      } else {
        dp[i + 1][j] += dp[i][j];
        dp[i + 1][j] %= MOD;
      }
      if (j != 0) dp[i + 1][j] += dp[i + 1][j - 1];

      dp[i + 1][j] %= MOD;
    }
  }

  cout << dp[N][K] << endl;

  return 0;
}