//
//
//  Codeforces: ganariya
//  AtCoder: ganariya2525
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//include
//------------------------------------------
#include <vector>
#include <list>
#include <map>
#include <unordered_map>
#include <climits>
#include <set>
#include <unordered_set>
#include <deque>
#include <stack>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <string>
#include <cstring>
#include <ctime>
#include <queue>
#include <random>
#include <complex>
#include <regex>
#include <locale>
#include <random>
#include <type_traits>

using namespace std;

#define SHOW_VECTOR(v) {std::cerr << #v << "\t:";for(const auto& xxx : v){std::cerr << xxx << " ";}std::cerr << "\n";}
#define SHOW_MAP(v){std::cerr << #v << endl; for(const auto& xxx: v){std::cerr << xxx.first << " " << xxx.second << "\n";}}

using LL = long long;

//~~~~~~~~~~~~~~~~~~~~~_(＾～＾ ｣ ∠)_~~~~~~~~~~~~~~~~~~~~~

constexpr LL mod = 1e9 + 7;

int main() {

    int N, K;
    cin >> N >> K;

    vector<LL> a(N);
    for (int i = 0; i < N; i++) cin >> a[i];

    //dp[i + 1][j]
    //[0, i)人目まででj個のアメを分けあうときの通り数
    vector<vector<LL>> dp(N + 1, vector<LL>(K + 1, 0));
    dp[0][0] = 1;

    for (int i = 0; i < N; i++) {
        vector<LL> pSum(K + 2, 0);
        for (int j = 0; j <= K; j++) pSum[j + 1] = (pSum[j] + dp[i][j]) % mod;
        for (LL j = 0; j <= K; j++) {
            dp[i + 1][j] = pSum[j + 1] - pSum[max(0LL, j - a[i])];
            dp[i + 1][j] = (dp[i + 1][j] + mod) % mod;
        }
    }

    cout << dp[N][K] << endl;

    return 0;
}
















































Measured memory_bytes: 80256