#include <bits/stdc++.h>
#include <algorithm>
using namespace std;

#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace __gnu_pbds;
template<typename T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
#define int long long
#define ll long long
#define ull unsigned long long
#define ld long double
#define yes cout << "YES"<<'\n';
#define no cout << "NO"<<'\n';
#define nl "\n"
#define sz(s) (int) (s).size()
#define fr(n) for (int i = 0; i < n; ++i)
#define aw3dni_ink_tet3aleg ios_base::sync_with_stdio(false), cout.tie(NULL), cin.tie(NULL);
// const double PI = 3.14159265358979323846264338327950288419716939937510L;;
#define sp(x) fixed << setprecision(x)
#define all(v) v.begin(), v.end()
#define ff first
#define ss second
#define pii pair<ll,ll>
#define put(x) return void(cout << x)
#define all(v) v.begin(), v.end()
#define allr(v) v.rbegin(), v.rend()
#define cin(vec)                                                                                                       \
    for (auto &i: vec)                                                                                                 \
    cin >> i
#define cout(vec)                                                                                                      \
    for (auto &i: vec)                                                                                                 \
        cout << i << " ";                                                                                              \
    cout << "\n";
#define ON(n, k) ((n) | (1ll << (k)))
#define OFF(n, k) ((n) & ~(1ll << (k)))
#define isON(n, k) (((n) >> (k)) & 1)
#define flip(n, k) ((n) ^ (1ll << (k)))
#define popcnt(x) (__builtin_popcountll(x))

template<typename T = int>
istream &operator>>(istream &in, vector<T> &v) {
    for (auto &x: v)in >> x;
    return in;
}

template<typename T = int>
ostream &operator<<(ostream &out, const vector<T> &v) {
    for (const T &x: v)out << x << ' ';
    return out;
}

void FILES() {
    aw3dni_ink_tet3aleg
    // freopen("angle3.in", "r", stdin);
    // freopen("angle3.out", "w", stdout);
}

#define ceil_i(a, b) (((ll) (a) + (ll) (b - 1)) / (ll) (b))
#define floor_i(a, b) (a / b)
#define round_i(a, b) ((a + (b / 2)) / b)

ll OO = 1e17, MOD = 1e9 + 7; //1e9 + 7 ,,998244353

// int add(int a, int b) { return ((a % MOD) + (b % MOD) + MOD) % MOD; }

// int mul(int a, int b) { return (((a % MOD) * (b % MOD))) % MOD; }
int add(int a, int b) {
    if (a < 0)
        a += MOD;
    if (a >= MOD)
        a -= MOD;
    if (b < 0)
        b += MOD;
    if (b >= MOD)
        b -= MOD;
    if (a + b >= MOD)
        return a + b - MOD;
    return a + b;
}

// int add(int a, int b) {
//     return (0ll + a + b + MOD) % MOD;
// }
int sub(int a, int b) {
    return add(a, -b);
}

int mul(int a, int b) {
    return (1ll * a * b) % MOD;
}

// int sub(int a, int b) { return (((a % MOD) - (b % MOD)) + MOD) % MOD; }


#define INF 1e18

int dx[] = {1, 0, -1, 0, -1, -1, 1, 1};
int dy[] = {0, -1, 0, 1, -1, 1, -1, 1};
char di[] = {'D', 'L', 'U', 'R'};
// up right down left

const int N = 1e3 + 5, X = 505, EPS = 1e-12;

// وَقُلْ رَبِّ زِدْنِي عِلْمًا
// typedef ll T;
// typedef complex<T> pt;
// #define x real()
// #define y imag()
ll fact[N + 1], inv_fact[N + 1];
ll modPow(ll x, ll n, ll mod) {
    x %= mod;
    ll res = 1;
    while (n > 0) {
        if (n % 2) res = res * x % mod;
        x = x * x % mod;
        n /= 2;
    }
    return res;
}
 
int modInverse(int a, int m) {
    /// m==>MOD
    // eq = c*(a^-1)-- c is Numerator --- a is Denominator
    //a==>mod inverse
    // use mull(c,modInvers)
    return modPow(a, m - 2, MOD);
}
 
void factorial() {
    fact[0] = 1;
    for (int i = 1; i <= N; i++) fact[i] = fact[i - 1] * i % MOD;
}
 
void inv_factorial() {
    inv_fact[N] = modPow(fact[N], MOD - 2, MOD);
    for (int i = N; i >= 1; i--) inv_fact[i - 1] = inv_fact[i] * i % MOD;
}
 
ll NCR(ll n, ll r) {
    if (r < 0 || r > n) return 0;
    return fact[n] * inv_fact[r] % MOD * inv_fact[n - r] % MOD;
}
 
void pre_count() {
    factorial();
    inv_factorial();
}
int n , k ;
ll arr[N],dp[N][X];
ll calc(int idx , int rem){
    if(idx==n)
        return rem==0;
    int &ret = dp[idx][rem];
    if(~ret)
     return ret;
    ret = 0;
    for(int i = 0;i<=min(rem,arr[i]-1);i++){
        if(rem>=i)
            ret =add(ret,mul(NCR(arr[i],i),calc(idx+1,rem-i)));
    }
    return ret;
}
void solve() {
    cin >> n >> k ;
    for(int i = 0 ; i<n ; i++){
        cin >>arr[i];
    }
    memset(dp,-1,sizeof(dp));
    ll ans = calc(0,k);
    cout << ans;
}


signed main() {
    //=========================================================================
    FILES();
    //=========================================================================
    int T = 1, t = 1;
    // phi_1_to_n();
    // linear_sieve(1e6);
    pre_count();
    // sieve();
    // PascalPyramid();
    // computeCatalan();
    // preprocess(50);
    // totient_sieve();
    // cin >> T;
    while (T--) {
        solve();
        t++;
        // vid++;
        cout << nl;
    }
    return 0;
}