#include <bits/stdc++.h>
#define int long long int
using namespace std;
template<typename T,typename U> using P=pair<T,U>;
template<typename T> using V=vector<T>;
template<typename T>bool chmax(T&a,T b){if(a<b){a=b;return true;}return false;}
template<typename T>bool chmin(T&a,T b){if(a>b){a=b;return true;}return false;}

template<typename T>auto&operator<<(ostream&s,const vector<T>&v){s<<"[";bool a=1;for(auto e:v){s<<(a?"":" ")<<e;a=0;}s<<"]";return s;}
template<typename T,typename U>auto&operator<<(ostream&s,const pair<T,U>&p){s<<"("<<p.first<<","<<p.second<<")";return s;}
template<typename T>auto&operator<<(ostream&s,const set<T>&st){s<<"{";bool a=1;for(auto e:st){s<<(a?"":" ")<<e;a=0;}s<<"}";return s;}
template<typename T,typename U>auto&operator<<(ostream&s,const map<T,U>&m){s<<"{";bool a=1;for(auto e:m){s<<(a?"":" ")<<e.first<<":"<<e.second;a=0;}s<<"}";return s;}
#define DUMP(x)  cerr<<#x<<" = "<<(x)<<endl;

struct edge { int to, cost; };

const int INF = 1e18;
const int MOD = 1e9+7;

struct ModRing {
   int mod, x;
   ModRing(int mod_n) : mod(mod_n), x(0) {}
   ModRing(int a, int mod_n) : mod(mod_n) { x = ((a % mod) + mod) % mod; }

   bool operator==(const ModRing& a) const {
      return x == a.x;
   }
   bool operator==(int a) const {
      return *this == ModRing(a, mod);
   }
   ModRing& operator=(int a) {
      return *this = ModRing(a, mod);
   }
   ModRing operator-() const {
      return ModRing((-x + mod) % mod, mod);
   }
   ModRing& operator+=(const ModRing& a) {
      (x += a.x) %= mod;
      return *this;
   }
   ModRing& operator-=(const ModRing& a) {
      return *this += -a;
   }
   ModRing& operator*=(const ModRing& a) {
      (x *= a.x) %= mod;
      return *this;
   }
   const ModRing operator+(const ModRing& a) const {
      return ModRing(x, mod) += a;
   }
   const ModRing operator-(const ModRing& a) const {
      return ModRing(x, mod) -= a;
   }
   const ModRing operator*(const ModRing& a) const {
      return ModRing(x, mod) *= a;
   }
   ModRing& operator+=(int a) {
      return *this += ModRing(a, mod);
   }
   ModRing& operator-=(int a) {
      return *this -= ModRing(a, mod);
   }
   ModRing& operator*=(int a) {
      return *this *= ModRing(a, mod);
   }
   const ModRing operator+(int a) const {
      return ModRing(x, mod) += a;
   }
   const ModRing operator-(int a) const {
      return ModRing(x, mod) -= a;
   }
   const ModRing operator*(int a) const {
      return ModRing(x, mod) *= a;
   }
   ModRing power(int n) const {
      ModRing tmp(x, mod), res(1, mod);
      while (n > 0) {
         if ((n & 1) == 1) res *= tmp;
         tmp *= tmp;
         n >>= 1;
      }
      return res;
   }
};
auto&operator<<(ostream&s,const ModRing&a){s<<a.x;return s;}

struct FiniteField : ModRing {
   FiniteField(int mod_n) : ModRing(mod_n) {}
   FiniteField(int a, int mod_n) : ModRing(a, mod_n) {}
   FiniteField(const ModRing& a) : ModRing(a) {}

   bool operator==(const FiniteField& a) const {
      return ModRing::operator==(a);
   }
   bool operator==(int a) const {
      return ModRing::operator==(a);
   }
   FiniteField& operator=(int a) {
      return *this = FiniteField(ModRing::operator=(a));
   }
   FiniteField operator-() const {
      return FiniteField(ModRing::operator-());
   }
   FiniteField& operator+=(const FiniteField& a) {
      return *this = FiniteField(ModRing::operator+=(a));
   }
   FiniteField& operator-=(const FiniteField& a) {
      return *this = FiniteField(ModRing::operator-=(a));
   }
   FiniteField& operator*=(const FiniteField& a) {
      return *this = FiniteField(ModRing::operator*=(a));
   }
   const FiniteField operator+(const FiniteField& a) const {
      return FiniteField(ModRing::operator+(a));
   }
   const FiniteField operator-(const FiniteField& a) const {
      return FiniteField(ModRing::operator-(a));
   }
   const FiniteField operator*(const FiniteField& a) const {
      return FiniteField(ModRing::operator*(a));
   }
   FiniteField& operator+=(int a) {
      return *this = FiniteField(ModRing::operator+=(a));
   }
   FiniteField& operator-=(int a) {
      return *this = FiniteField(ModRing::operator-=(a));
   }
   FiniteField& operator*=(int a) {
      return *this = FiniteField(ModRing::operator*=(a));
   }
   const FiniteField operator+(int a) const {
      return FiniteField(ModRing::operator+(a));
   }
   const FiniteField operator-(int a) const {
      return FiniteField(ModRing::operator-(a));
   }
   const FiniteField operator*(int a) const {
      return FiniteField(ModRing::operator*(a));
   }
   FiniteField power(int n) const {
      return FiniteField(ModRing::power(n));
   }

   FiniteField inverse() const {
      try { if (x == 0) throw "0 have no inverse"; }
      catch (const char* e) { cerr << e << endl; }
      return power(mod-2);
   }
   FiniteField& operator/=(const FiniteField& a) {
      return *this *= a.inverse();
   }
   const FiniteField operator/(const FiniteField& a) const {
      return FiniteField(x, mod) /= a;
   }
   FiniteField& operator/=(int a) {
      return *this /= FiniteField(a, mod);
   }
   const FiniteField operator/(int a) const {
      return FiniteField(x, mod) /= a;
   }
};

int GF_MOD = MOD;
struct GF : FiniteField {
   GF() : FiniteField(GF_MOD) {}
   GF(int a) : FiniteField(a, GF_MOD) {}
   GF(const FiniteField& a) : FiniteField(a) {}
};

signed main()
{
   int n, K; cin >> n >> K;
   V<int> a(n);
   for (int i = 0; i < n; i++) {
      cin >> a[i];
   }

   V<V<GF>> dp(n+1, V<GF>(K+1));
   V<V<GF>> sum(n+1, V<GF>(K+2));
   dp[0][0] = 1;
   for (int k = 0; k <= K; k++) {
      sum[0][k+1] = sum[0][k] + dp[0][k];
   }
   for (int i = 0; i < n; i++) {
      for (int k = 0; k <= K; k++) {
         dp[i+1][k] = sum[i][k+1] - sum[i][max(k-a[i], 0LL)];
         sum[i+1][k+1] = sum[i+1][k] + dp[i+1][k];
      }
   }
   cout << dp[n][K] << endl;

   return 0;
}


Measured memory_bytes: 317540