#include<iostream>
#include<vector>
using namespace std;
 
class ModInt{
private:
  long long val;
  static const int default_mod = 1e9 + 7;
  static int mod;
  static vector<ModInt> facts;
public:
  ModInt(long long val)
  {
    if(mod == 0){
      mod = default_mod;
    }
    this->val = ((val % mod) + mod) % mod;
  }
  ModInt()
    : ModInt(0)
  {
  }
  static void setMod(int mod){
    if(ModInt::mod != 0){
      throw "The modulo is already set.";
    }
    ModInt::mod = mod;
  }

  const ModInt operator* (const ModInt& another) const{
    return ModInt(val * another.val);
  }
  ModInt operator+ (const ModInt& another){
    return ModInt(val + another.val);
  }
  ModInt operator- (const ModInt & another){
    return ModInt(val - another.val + mod);
  }
  ModInt operator/(const ModInt& rhs){
    return (*this) * rhs.inv();
  }
  ModInt& operator*=(const ModInt& rhs){
    (*this) = (*this) * rhs;
    return *this;
  }
  ModInt& operator+=(const ModInt& rhs){
    (*this) = (*this) + rhs;
    return *this;
  }
  ModInt& operator-=(const ModInt& rhs){
    (*this) = (*this) - rhs;
    return *this;
  }
  ModInt& operator/=(const ModInt& rhs){
    (*this) = (*this) / rhs;
    return *this;
  }
  ModInt pow(long long exponent) const{
    exponent %= mod - 1;
    if(exponent == 0){
      return ModInt(1);
    }else{
      if(exponent % 2){
        return ((*this) * (*this)).pow(exponent / 2) * (*this);
      }else{
        return ((*this) * (*this)).pow(exponent / 2);
      }
    }
  }
  ModInt inv() const{
    return this->pow(mod - 2);
  }
  static ModInt fact(long long n){
    if(n >= mod){
      return 0;
    }
    if(facts.size() < static_cast<size_t>(n + 1)){
      if(facts.size() == 0){
        facts.push_back(1);
      }
      for(int i = facts.size(); i <= n; i++){
        facts.push_back(facts[i - 1] * i);
      }
    }
    return facts[n];
  }
  static ModInt comb(long long n, long long r){
    if(r > n){
      return 0;
    }
    return ModInt::fact(n) * ModInt::fact(r).inv() * ModInt::fact(n - r).inv();
  }
 
  friend ostream& operator<< (ostream& os, const ModInt& modint){
    os << modint.val;
    return os;
  }
  friend istream& operator>>(istream& is, ModInt& modint){
    long long val;
    is >> val;
    modint.val = val % modint.mod;
    return is;
  }
  friend ModInt operator*(const long long lhs, const ModInt& rhs){
    return ModInt(lhs) * rhs;
  }
};
int ModInt::mod = 0;
vector<ModInt> ModInt::facts;

int main(){
  int N, K;
  cin >> N >> K;

  vector<int> a(N);
  for(auto& aa: a){
    cin >> aa;
  }

  // dp[n][k] := #{(c[0], ..., c[n - 1])| c[i] <= a[i], sum of c[i] = k}
  // dp[n][k] = dp[n - 1][k] + ... + dp[n - 1][k - a[n - 1]]
  vector<vector<ModInt>> dp(N + 1, vector<ModInt>(K + 1));
  dp[0][0] = 1;
  for(int n = 1; n <= N; n++){
    dp[n][0] = 1;
    // memo[k] := dp[n - 1][0] + ... + dp[n - 1][k - 1]
    vector<ModInt> memo(K + 2);
    memo[0] = 0;
    for(int k = 1; k <= K + 1; k++){
      memo[k] = memo[k - 1] + dp[n - 1][k - 1];
    }
    for(int k = 1; k <= K; k++){
      dp[n][k] = memo[k + 1] - memo[max(0, k - a[n - 1])];
    }
  }
  /*
  for(int n = 0; n <= N; n++){
    for(int k = 0; k <= K; k++){
      cout << dp[n][k] << ' ';
    }cout << endl;
  }
  */
  cout << dp[N][K] << endl;
  
}


Measured memory_bytes: 80256