#define _GLIBCXX_DEBUG
#include<bits/stdc++.h>
using namespace std;
#define rep(i,x) for(ll i = 0; i < (ll)(x); i++)
#define rrep(i,x) for(ll i = (ll)(x)-1;0 <= i; i--)
#define reps(i,x) for(ll i = 1; i < (ll)(x)+1; i++)
#define rreps(i,x) for(ll i = (ll)(x); 1 <= i; i--)
#define debug(x) cerr << #x << ": " << (x) << "\n";
#define all(x) (x).begin(), (x).end()
typedef long long ll;
typedef long double ld;
typedef pair<int,int> P;
typedef pair<ll,ll> Pll;
typedef vector<ll> vl;
typedef vector<vector<ll>> vvl;
typedef vector<vector<vector<ll>>> vvvl;
const ll INF = numeric_limits<ll>::max()/4;
const int n_max = 1e5+10;
#define int ll

void print() {
    cout << endl;
}

// template <class Head, class... Tail>
// void print(Head&& head, Tail&&... tail) {
//     cout << head;
//     if (sizeof...(tail) != 0) cout << " ";
//     print(forward<Tail>(tail)...);
// }

template <class T>
void print(vector<T> &vec) {
    for (auto& a : vec) {
        cout << a;
        if (&a != &vec.back()) cout << " ";
    }
    cout << endl;
}

template <class T>
void print(vector<T> &vec, ll k){
   ll n = vec.size();
   k = min(k, n);
   rep(i,k-1)cout << vec[i] << " ";
   cout << vec[k-1] << endl;
}

template <class T>
void print(vector<vector<T>> &df) {
    for (auto& vec : df) {
        print(vec);
    }
}

template<class T, class U>
void print(pair<T,U> &p){
    cout << p.first << " " << p.second << "\n";
}


template<std::int_fast64_t Modulus>
class modint {
    using i64 = int_fast64_t;

    public:
    i64 a;

    constexpr modint(const i64 x = 0) noexcept {
        this -> a = x % Modulus;
        if(a < 0){
            a += Modulus;
        }
    }
    constexpr int getmod() { return Modulus; }
    constexpr modint operator - () const noexcept {
        return a ? Modulus - a : 0;
    }
    // constexpr i64 &value() const noexcept {return a;}
    constexpr const i64 &value() const noexcept {return a;}
    constexpr modint operator+(const modint rhs) const noexcept {
        return modint(*this) += rhs;
    }
    constexpr modint operator-(const modint rhs) const noexcept {
        return modint(*this) -= rhs;
    }
    constexpr modint operator*(const modint rhs) const noexcept {
        return modint(*this) *= rhs;
    }
    constexpr modint operator/(const modint rhs) const noexcept {
        return modint(*this) /= rhs;
    }
    constexpr modint &operator+=(const modint rhs) noexcept {
        a += rhs.a;
        if(a >= Modulus) {
            a -= Modulus;
        }
        return *this;
    }
    constexpr modint &operator-=(const modint rhs) noexcept {
        if(a < rhs.a) {
            a += Modulus;
        }
        a -= rhs.a;
        return *this;
    }
    constexpr modint &operator*=(const modint rhs) noexcept {
        a = a * rhs.a % Modulus;
        return *this;
    }
    constexpr modint &operator/=(modint rhs) noexcept {
        i64 a_ = rhs.a, b = Modulus, u = 1, v = 0;
        while(b){
            i64 t = a_/b;
            a_ -= t * b; swap(a_,b);
            u -= t * v; swap(u,v);
        }
        a = a * u % Modulus;
        if(a < 0) a += Modulus;
        return *this;
    }
    
    // 自前実装
    constexpr bool operator==(const modint rhs) noexcept {
        return a == rhs.a;
    }
    constexpr bool operator!=(const modint rhs) noexcept {
        return a != rhs.a;
    }
    constexpr bool operator>(const modint rhs) noexcept {
        return a > rhs.a;
    }
    constexpr bool operator>=(const modint rhs) noexcept {
        return a >= rhs.a;
    }
    constexpr bool operator<(const modint rhs) noexcept {
        return a < rhs.a;
    }
    constexpr bool operator<=(const modint rhs) noexcept {
        return a <= rhs.a;
    }
    // constexpr modint& operator++() noexcept {
    //     return (*this) += modint(1);
    // }
    // constexpr modint operator++(int) {
    //     modint tmp(*this);
    //     operator++();
    //     return tmp;
    // }
    // constexpr modint& operator--() noexcept {
    //     return (*this) -= modint(1);
    // }
    // constexpr modint operator--(int) {
    //     modint tmp(*this);
    //     operator--();
    //     return tmp;
    // }
    template<typename T>
    friend constexpr modint modpow(const modint &mt, T n) noexcept {
        if(n < 0){
            modint t = (modint(1) / mt);
            return modpow(t, -n);
        }
        modint res = 1, tmp = mt;
        while(n){
            if(n & 1)res *= tmp;
            tmp *= tmp;
            n /= 2;
        }
        return res;
    }
};

const ll MOD = 1e9+7;
using mint = modint<MOD>;
// 標準入出力対応
std::ostream &operator<<(std::ostream &out, const modint<MOD> &m) {
    out << m.a;
    return out;
}
std::istream &operator>>(std::istream &in, modint<MOD> &m) {
    ll a;
    in >> a;
    m = mint(a);
    return in;
}


signed main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    ll n,k; cin >> n >> k;
    vector<ll> a(n);
    rep(i,n) cin >> a[i];
    vector<vector<mint>> dp(n+1, vector<mint>(k+1));
    dp[0][0] = 1;
    vector<mint> sum(k+2);
    rep(i,n){
        rep(j, k+1)sum[j+1] = sum[j] + dp[i][j];
        rep(j,k+1){
            dp[i+1][j] = sum[j+1] - sum[max(0LL, j - a[i])];
        }
    }
    // print(dp);
    cout << dp[n][k] << endl;
}

Measured memory_bytes: 80256