#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using vl = vector<ll>;
using vvl = vector<vector<ll>>;
using pl = pair<ll, ll>;
using vpl = vector<pl>;
using vvpl = vector<vpl>;
const ll MOD = 1000000007;
const ll MOD9 = 998244353;
const int inf = 1e9 + 10;
const ll INF = 4e18;
const ll dy[9] = {1, 0, -1, 0, 1, 1, -1, -1, 0};
const ll dx[9] = {0, -1, 0, 1, 1, -1, 1, -1, 0};
template <class T>
inline bool chmin(T& a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <class T>
inline bool chmax(T& a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
const int mod = 1000000007;
const int max_n = 200005;
struct mint {
  ll x;
  mint(ll x = 0) : x((x % mod + mod) % mod) {}
  mint operator-() const { return mint(-x); }
  mint& operator+=(const mint a) {
    if ((x += a.x) >= mod) x -= mod;
    return *this;
  }
  mint& operator-=(const mint a) {
    if ((x += mod - a.x) >= mod) x -= mod;
    return *this;
  }
  mint& operator*=(const mint a) {
    (x *= a.x) %= mod;
    return *this;
  }
  mint operator+(const mint a) const { return mint(*this) += a; }
  mint operator-(const mint a) const { return mint(*this) -= a; }
  mint operator*(const mint a) const { return mint(*this) *= a; }
  mint pow(ll t) const {
    if (!t) return 1;
    mint a = pow(t >> 1);
    a *= a;
    if (t & 1) a *= *this;
    return a;
  }
  mint inv() const { return pow(mod - 2); }
  mint& operator/=(const mint a) { return *this *= a.inv(); }
  mint operator/(const mint a) const { return mint(*this) /= a; }
};
istream& operator>>(istream& is, mint& a) { return is >> a.x; }
ostream& operator<<(ostream& os, const mint& a) { return os << a.x; }
int main() {
  ll n, k;
  cin >> n >> k;
  vl a(n);
  for (ll i = 0; i < n; i++) cin >> a[i];
  vector<vector<mint>> dp(n + 1, vector<mint>(k + 1)),
      cum(n + 1, vector<mint>(k + 2));
  dp[0][0] = 1;
  for (ll i = 0; i < k + 2; i++) cum[0][i] = 1;
  cum[0][0] = 0;
  for (ll i = 0; i < n; i++) {
    for (ll j = 0; j < k + 1; j++) {
      dp[i + 1][j] += cum[i][j + 1];
      if (j - a[i] >= 0) dp[i + 1][j] -= cum[i][j - a[i]];
    }
    for (ll j = 0; j < k + 2; j++)
      cum[i + 1][j + 1] += cum[i + 1][j] + dp[i + 1][j];
  }
  cout << dp[n][k] << endl;
}
