#include <iostream>
#include <iosfwd>
#include <iomanip>
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <ctime>
#include <cmath>
#include <cassert>
#include <cctype>
#include <climits>
#include <vector>
#include <bitset>
#include <set>
#include <queue>
#include <stack>
#include <map>
#include <deque>
#include <string>
#include <list>
#include <iterator>
#include <sstream>
#include <complex>
#include <fstream>
#include <functional>
#include <numeric>
#include <utility>
#include <algorithm>

using namespace std;

// MACROS_BEGIN
#define CLEAR() cerr << endl;
#define LET(x, a) __typeof(a) x = a
#define FOREACH(it, v) for (LET(it, (v).begin()); it != (v).end(); ++it)
#define REPEAT(i, n) for (int i = 0; i < (n); ++i)
// MACROS_END

// GENERIC_UTILITIES_BEGIN
template <class T> inline int size(const T& c) {return (int) c.size();}
inline long long two(int x) {return (1LL << (x));}

vector<string> split(string s, string delim) {
    s += delim[0];
    string tmp;
    vector<string> result;
    for (int i = 0; i < size(s); ++i) {
        if (delim.find(s[i]) == string::npos) {
            tmp.push_back(s[i]);
        }
        else {
            if (tmp != "") result.push_back(tmp);
            tmp.clear();
        }
    }
    return result;
}

template <class A, class B> void setMin(A& a, const B& b) {
    a = min(a, b);
}

template <class A, class B> void setMax(A& a, const B& b) {
    a = max(a, b);
}
// GENERIC_UTILITIES_END

// FAST_IO_BEGIN
// FAST_IO_END

// STANDARD_IO_BEGIN
#ifndef USING_FAST_IO
int readInt() {int N = -1; scanf("%d", &N); return N;}
double readDouble() {double D; scanf("%lf", &D); return D;}
string readString() {char buffer[1 << 20]; scanf("%s", buffer); return buffer;}
long long readLongLong() {long long N = -1; scanf("%lld", &N); return N;}
#endif // NOT DEFINED USING_FAST_IO
// STANDARD_IO_END


// OUTPUT_UTILITIES_BEGIN
template <class A, class B> ostream& operator << (ostream& o, const pair<A, B>& p);
template <class T> ostream& operator << (ostream& o, const vector<T>& v);
template <class A, class B> ostream& operator << (ostream& o, const map<A, B>& m);
template <class T> ostream& operator << (ostream& o, const set<T>& s);
template <class T> ostream& operator << (ostream& o, const queue<T>& q);
template <class T> ostream& operator << (ostream& o, const stack<T>& s);

template <class A, class B> ostream& operator << (ostream& o, const pair<A, B>& p) {
    o << "(" << p.first << "," << p.second << ")"; return o;
}

template <class T> ostream& operator << (ostream& o, const vector<T>& v) {
    o << "{"; bool first = true; FOREACH(it, v) { if (!first) o << ","; first = false; o << *it; } return o << "}";
}

template <class A, class B> ostream& operator << (ostream& o, const map<A, B>& m) {
    o << "{"; bool first = true; FOREACH(it, m) { if (!first) o << ","; first = false; o << *it; } return o << "}";
}

template <class T> ostream& operator << (ostream& o, const set<T>& s) {
    o << "{"; bool first = true; FOREACH(it, s) { if (!first) o << ","; first = false; o << *it; } return o << "}";
}

template <class T> ostream& operator << (ostream& o, const queue<T>& q) {
    o << "{"; bool first = true; queue<T> p = q; while (!p.empty()) { if (!first) o << ","; first = false; o << p.front(); p.pop(); } return o << "}";
}

template <class T> ostream& operator << (ostream& o, const stack<T>& s) {
    o << "{"; bool first = true; stack<T> r = s; while (!r.empty()) { if (!first) o << ","; first = false; o << r.top(); r.pop(); } return o << "}";
}
// OUTPUT_UTILITIES_END

// DEBUGGING_UTILITIES_BEGIN
// DEBUGGING SWITCH
#define PHOENIX_DEBUG

#ifdef PHOENIX_DEBUG
#define BUG(x) cerr << __LINE__ << ": " << #x << " = " << x << endl;
#else
#define BUG(...)
#endif
// DEBUGGING_UTILITIES_END

const double epsilon = 1e-8;
const int infinite    = 1000000000;
const long long infiniteLL = 1000000000000000000LL;
const long long modulo = 1000000007;

struct Solver {
    int N, K;

    void add(long long& x, long long y) {
        x += y;

        if (x >= modulo) {
            x -= modulo;
        }
    }

    void sub(long long& x, long long y) {
        x -= y;

        if (x < 0) {
            x += modulo;
        }
    }

    void process(vector<long long>& dp, int K, int c) {
        vector<long long> next(K + 1, 0);
        next = dp;
        vector<long long> prefix(K + 1, 0);

        for (int used = K; used >= 0; --used) {
            long long tmp = dp[used];
            int L = used + 1;
            int R = used + min(c, K - used);

            if (L <= R) {
                add(prefix[L], tmp);

                if (R + 1 < size(prefix)) {
                    sub(prefix[R + 1], tmp);
                }
            }
        }

        long long prefixSum = 0;

        for (int i = 0; i < size(next); ++i) {
            add(prefixSum, prefix[i]);
            add(next[i], prefixSum);
        }

        dp = next;
    }

    long long solve(int _N, int _K, vector<int>& a) {
        N = _N;
        K = _K;

        vector<long long> dp(K + 1, 0);
        dp[0] = 1;

        for (int i = 0; i < N; ++i) {
            process(dp, K, a[i]);
        }

        return dp[K];
    }
};

int main()
{
    int nTest = 1;

    for (int test = 1; test <= nTest; ++test) {
        int N = readInt(), K = readInt();
        vector<int> a(N);

        for (int i = 0; i < N; ++i) {
            a[i] = readInt();
        }

        Solver solver;
        long long result = solver.solve(N, K, a);

        cout << result << endl;
    }

    return 0;
}

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Measured memory_bytes: 2644