#include <bits/stdc++.h>
using ull = unsigned long long int;
using ll = long long;
using ld = long double;
using pii = std::pair<int, int>;
using pll = std::pair<ll, ll>;
using vi = std::vector<int>;
using vvi = std::vector<vi>;
using vll = std::vector<ll>;
using vvll = std::vector<vll>;
using vd = std::vector<double>;
using vvd = std::vector<vd>;
using qi = std::queue<int>;
using vpii = std::vector<std::pair<int, int>>;
using vpll = std::vector<pll>;
using namespace std;
const int Mod = (1e9) + 7;
const int INF = 1e9 + 19;
const ll INFL = 1e18 + 19;
const int dx[] = {-1, 0, 0, 1};
const int dy[] = {0, -1, 1, 0};
const int dx2[] = {-1, -1, -1, 0, 0, 0, 1, 1, 1};
const int dy2[] = {1, 0, -1, 1, 0, -1, 1, 0, -1};
template <class T1, class T2>
inline void chmin(T1& a, T2 b) {
  if (a > b) a = b;
}
template <class T1, class T2>
inline void chmax(T1& a, T2 b) {
  if (a < b) a = b;
}
template <class T>
inline void pri(T a) {
  cout << a << endl;
}
template <class Z>
using vec = vector<Z>;
template <class T>
using min_priority_queue = priority_queue<T, vector<T>, greater<T>>;
template <class T1, class T2>
void update(T1& a, T2 b) {
  a += b;
  if (a > Mod) a %= Mod;
}
inline void IN(void) { return; }
template <typename First, typename... Rest>
void IN(First& first, Rest&... rest) {
  cin >> first;
  IN(rest...);
  return;
}
inline void OUT(void) {
  cout << "\n";
  return;
}
template <typename First, typename... Rest>
void OUT(First first, Rest... rest) {
  cout << first << " ";
  OUT(rest...);
  return;
}
bool pairsort(pll pl, pll pr) {
  if (pl.first == pr.first) return pl.second > pr.second;
  return pl.first < pr.first;
}
int cntbit(ll a, int n, int j) {
  int res = 0;
  for (int(i) = (j); (i) < (n); (i)++) {
    if (a >> i & 1) {
      res++;
    }
  }
  return res;
}
vector<int> make_bit(int a) {
  vector<int> res;
  for (int i = 0; i < (32); i++)
    if (a & (1 << i)) res.push_back(i);
  return res;
}
bool stdbit(int a, int b) { return a & (1 << b); }
int GCD(int a, int b) {
  if (b > a) return GCD(b, a);
  if (a % b == 0)
    return b;
  else
    return GCD(b, a % b);
}
int LCM(int a, int b) { return a * b / GCD(a, b); }
int roundup(int a, int b) {
  if (a % b == 0)
    return a / b;
  else
    return (a + b) / b;
}
int rounddown(int a, int b) {
  if (a % b == 0)
    return a / b;
  else {
    return (a - b) / b;
  }
}
ll pow(ll a, ll n) {
  ll res = 1;
  while (n > 0) {
    if (n & 1) res *= a;
    a *= a;
    n = n >> 1;
  }
  return res;
}
ll GetDiviserCount(ll N) {
  ll res = 1;
  for (int(i) = (2); (i) < (sqrt(N) + 1); (i)++) {
    ll cnt = 0;
    while (N % i == 0) {
      cnt++;
      N /= i;
    }
    res *= (cnt + 1);
    if (N == 1) break;
  }
  if (N != 1) res *= 2;
  return res;
}
vll GetDivisor(ll N) {
  vll res;
  for (ll i = 1; i * i <= N; i++) {
    if (N % i == 0) {
      res.push_back(i);
      if (i * i != N) res.push_back(N / i);
    }
  }
  sort((res).begin(), (res).end());
  return res;
}
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 {
    mint res(*this);
    return res += a;
  }
  mint operator-(const mint a) const {
    mint res(*this);
    return res -= a;
  }
  mint operator*(const mint a) const {
    mint res(*this);
    return res *= 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 {
    mint res(*this);
    return res /= a;
  }
  friend ostream& operator<<(ostream& os, const mint& a);
};
ostream& operator<<(ostream& os, const mint& a) {
  os << a.x;
  return os;
}
struct combination {
  vector<mint> fact, ifact;
  combination(int n) : fact(n + 1), ifact(n + 1) {
    assert(n < Mod);
    fact[0] = 1;
    for (int i = 1; i <= n; ++i) fact[i] = fact[i - 1] * i;
    ifact[n] = fact[n].inv();
    for (int i = n; i >= 1; --i) ifact[i - 1] = ifact[i] * i;
  }
  mint operator()(int n, int k) {
    if (k < 0 || k > n) return 0;
    return fact[n] * ifact[k] * ifact[n - k];
  }
};
const int max_n = 3 * (1e5) + 1;
const int max_m = 83 * (1e5) + 1;
int n, m, k;
ll N;
int h, w;
vvi tree;
string S;
int a, b, c;
vi v;
int ans;
signed main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  IN(n, k);
  vi a(n);
  for (int(i) = 0; (i) < (n); (i)++) IN(a[i]);
  vec<vec<mint>> dp(n + 1, vec<mint>(k + 1));
  vec<vec<mint>> sum(n + 1, vec<mint>(k + 1));
  for (int(i) = (max(0, k - a[0])); (i) < (k + 1); (i)++) {
    dp[0][i] = 1;
    sum[0][i + 1] = sum[0][i] + dp[0][i];
  }
  for (int(i) = (1); (i) < (n); (i)++) {
    for (int(j) = 0; (j) < (k + 1); (j)++) {
      dp[i][j] = sum[i - 1][min(k, j + a[i]) + 1] - sum[i - 1][j];
      sum[i][j + 1] = sum[i][j] + dp[i][j];
    }
  }
  mint ans = dp[n - 1][0];
  cout << ans << endl;
  return 0;
}
