#include <bits/stdc++.h>
using namespace std;
const int inf = 0x3f3f3f3f;
const int mod = 1e9 + 7;
void A() {
  int n;
  cin >> n;
  vector<int> a(n, 0);
  for (int i = 0; i < n; i++) cin >> a[i];
  vector<int> dp(n + 1, inf);
  dp[0] = 0;
  for (int i = 1; i < n; i++) {
    dp[i] = min(dp[i], dp[i - 1] + abs(a[i] - a[i - 1]));
    if (i >= 2) dp[i] = min(dp[i], dp[i - 2] + abs(a[i] - a[i - 2]));
  }
  cout << dp[n - 1] << endl;
}
void B() {
  int n, k;
  cin >> n >> k;
  vector<int> dp(n + 1, inf);
  vector<int> h(n, 0);
  for (int i = 0; i < n; i++) cin >> h[i];
  dp[0] = 0;
  for (int i = 1; i < n; i++) {
    for (int len = 1; len <= min(k + 1, i + 1); len++) {
      int j = i - len + 1;
      dp[i] = min(dp[i], dp[j] + abs(h[j] - h[i]));
    }
  }
  cout << dp[n - 1] << endl;
}
void C() {
  int n;
  cin >> n;
  vector<vector<int>> a(n, vector<int>(3, 0));
  for (int i = 0; i < n; i++) cin >> a[i][0] >> a[i][1] >> a[i][2];
  vector<vector<int>> dp(n, vector<int>(3, 0));
  dp[0][0] = a[0][0];
  dp[0][1] = a[0][1];
  dp[0][2] = a[0][2];
  for (int i = 1; i < n; i++) {
    for (int j = 0; j < 3; j++) {
      for (int k = 0; k < 3; k++) {
        if (j == k) continue;
        dp[i][j] = max(dp[i][j], dp[i - 1][k] + a[i][j]);
      }
    }
  }
  cout << max(dp[n - 1][0], max(dp[n - 1][1], dp[n - 1][2])) << endl;
}
void D() {
  long long n, W;
  cin >> n >> W;
  vector<pair<long long, long long>> p;
  for (int i = 0; i < n; i++) {
    long long a, b;
    cin >> a >> b;
    p.emplace_back(a, b);
  }
  sort(p.begin(), p.end());
  vector<long long> dp(W + 1, 0);
  for (int i = 0; i < n; i++) {
    for (int j = W; j >= p[i].first; j--) {
      if (j > 0) dp[j] = max(dp[j], dp[j - 1]);
      dp[j] = max(dp[j], dp[j - p[i].first] + p[i].second);
    }
  }
  cout << dp[W] << endl;
}
void E() {
  int n, W;
  cin >> n >> W;
  vector<long long> w(n, 0);
  vector<long long> v(n, 0);
  for (int i = 0; i < n; i++) cin >> w[i] >> v[i];
  vector<long long> dp(100005, inf);
  dp[0] = 0;
  int res = 0;
  for (int i = 0; i < n; i++) {
    for (int j = 1e5; j >= v[i]; j--) {
      dp[j] = min(dp[j], dp[j - v[i]] + w[i]);
      if (dp[j] <= W) {
        res = max(res, j);
      }
    }
  }
  cout << res << endl;
}
void F() {
  string s, t;
  cin >> s >> t;
  int n = s.size(), m = t.size();
  vector<vector<int>> dp(n + 1, vector<int>(m + 1, 0));
  for (int i = 1; i <= n; i++) {
    for (int j = 1; j <= m; j++) {
      char a = s[i - 1], b = t[j - 1];
      if (a == b) {
        dp[i][j] = max(dp[i][j], dp[i - 1][j - 1] + 1);
      }
      dp[i][j] = max(dp[i][j], max(dp[i - 1][j], dp[i][j - 1]));
    }
  }
  int i = n, j = m;
  stack<char> st;
  while (i != 0 && j != 0) {
    char a = s[i - 1], b = t[j - 1];
    if (a == b) {
      st.push(a);
      j--;
      i--;
    } else {
      if (dp[i][j] == dp[i - 1][j])
        i--;
      else
        j--;
    }
  }
  string res;
  while (!st.empty()) {
    res += st.top();
    st.pop();
  }
  cout << res << endl;
}
int Ghelper(vector<int>& dp, vector<vector<int>>& edge, int cur, int& ans) {
  if (dp[cur] != -1) return dp[cur];
  int res = 0;
  for (auto nb : edge[cur]) {
    res = max(res, Ghelper(dp, edge, nb, ans) + 1);
  }
  ans = max(ans, res);
  dp[cur] = res;
  return res;
}
void G() {
  int n, m;
  cin >> n >> m;
  vector<vector<int>> edge(n + 1, vector<int>());
  for (int i = 0; i < m; i++) {
    int x, y;
    cin >> x >> y;
    edge[x].push_back(y);
  }
  vector<int> dp(n + 1, -1);
  int res = 0;
  for (int i = 1; i <= n; i++) {
    Ghelper(dp, edge, i, res);
  }
  cout << res << endl;
}
void H() {
  int H, W;
  cin >> H >> W;
  vector<vector<char>> grid(H + 1, vector<char>(W + 1, '.'));
  vector<vector<long long>> dp(H + 1, vector<long long>(W + 1, 0));
  for (int i = 1; i <= H; i++) {
    for (int j = 1; j <= W; j++) {
      cin >> grid[i][j];
    }
  }
  dp[1][1] = 1;
  for (int i = 1; i <= H; i++) {
    for (int j = 1; j <= W; j++) {
      if (i == 1 && j == 1) continue;
      if (grid[i][j] == '#')
        dp[i][j] = 0;
      else {
        dp[i][j] = (dp[i - 1][j] + dp[i][j - 1]) % mod;
      }
    }
  }
  cout << dp[H][W] << endl;
}
void I() {
  int n;
  cin >> n;
  vector<vector<double>> dp(n + 1, vector<double>(n + 1, 0.0));
  vector<double> p(n, 0.0);
  for (int i = 0; i < n; i++) cin >> p[i];
  dp[0][0] = 1.0;
  for (int i = 1; i <= n; i++) {
    for (int j = 0; j <= i; j++) {
      if (j > 0) dp[i][j] += dp[i - 1][j - 1] * p[i - 1];
      dp[i][j] += dp[i - 1][j] * (1 - p[i - 1]);
    }
  }
  double res = 0.0;
  for (int i = (n + 1) / 2; i <= n; i++) res += dp[n][i];
  printf("%.10f\n", res);
}
double JHelper(vector<vector<vector<double>>>& dp, int a, int b, int c, int n) {
  if (a == 0 && b == 0 && c == 0) return 0;
  if (dp[a][b][c] > 0) return dp[a][b][c];
  double sum = a + b + c;
  double ans = 1.0 * n / sum;
  if (a) ans += JHelper(dp, a - 1, b, c, n) * (1.0 * a / sum);
  if (b) ans += JHelper(dp, a + 1, b - 1, c, n) * (1.0 * b / sum);
  if (c) ans += JHelper(dp, a, b + 1, c - 1, n) * (1.0 * c / sum);
  dp[a][b][c] = ans;
  return ans;
}
void J() {
  int n;
  cin >> n;
  vector<int> a(n, 0);
  for (int i = 0; i < n; i++) cin >> a[i];
  int cnt[4] = {0, 0, 0, 0};
  for (int i : a) {
    cnt[i]++;
  }
  vector<vector<vector<double>>> dp(
      n + 1, vector<vector<double>>(n + 1, vector<double>(n + 1, -1.0)));
  printf("%.13f\n", JHelper(dp, cnt[1], cnt[2], cnt[3], n));
}
void K() {
  int n, k;
  cin >> n >> k;
  vector<int> a(n + 1, 0);
  vector<int> dp(k + 3, -1);
  for (int i = 0; i < n; i++) {
    cin >> a[i];
  }
  dp[0] = 0;
  for (int i = 1; i <= k; i++) {
    dp[i] = 0;
    for (int j = 0; j < n && a[j] <= i; j++) {
      dp[i] |= 1 - dp[i - a[j]];
      if (dp[i] == 1) break;
    }
  }
  if (dp[k] == 1)
    cout << "First" << endl;
  else
    cout << "Second" << endl;
}
void L() {
  int n;
  cin >> n;
  vector<long long> a(n + 1, 0);
  for (int i = 1; i <= n; i++) cin >> a[i];
  vector<vector<long long>> dp(n + 2, vector<long long>(n + 2, 0));
  for (int len = 1; len <= n; len++) {
    for (int i = 1; i + len <= n + 1; i++) {
      int j = i + len - 1;
      if ((n - len) % 2 == 0) {
        dp[i][j] = max(dp[i + 1][j] + a[i], dp[i][j - 1] + a[j]);
      } else {
        dp[i][j] = min(dp[i + 1][j] - a[i], dp[i][j - 1] - a[j]);
      }
    }
  }
  cout << dp[1][n] << endl;
}
void M() {
  int n, K;
  cin >> n >> K;
  vector<int> a(n + 1, 0);
  for (int i = 1; i <= n; i++) cin >> a[i];
  vector<vector<int>> dp(n + 1, vector<int>(K + 1, 0));
  for (int i = 0; i <= n; i++) dp[i][0] = 1;
  for (int i = 1; i <= n; i++) {
    for (int j = 0; j < K; j++) {
      dp[i][j + 1] = (dp[i][j] + dp[i - 1][j + 1]) % mod;
      if (j >= a[i]) {
        dp[i][j + 1] = (dp[i][j + 1] - dp[i - 1][j - a[i]]) % mod;
      }
    }
  }
  cout << dp[n][K] << endl;
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  M();
}
