#include <iostream>
#include <cstdio>
#include <string>
#include <algorithm>
#include <utility>
#include <cmath>
#include <vector>
#include <stack>
#include <queue>
#include <deque>
#include <set>
#include <map>
#include <tuple>
#include <numeric>
#include <functional>
using namespace std;
typedef long long ll;
typedef vector<ll> vl;
typedef vector<vector<ll>> vvl;
typedef pair<ll, ll> P;
#define rep(i, n) for(ll i = 0; i < n; i++)
#define exrep(i, a, b) for(ll i = a; i <= b; i++)
#define out(x) cout << x << endl
#define exout(x) printf("%.10f\n", x)
#define chmax(x, y) x = max(x, y)
#define chmin(x, y) x = min(x, y)
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define pb push_back
#define re0 return 0
const ll mod = 1000000007;
const ll INF = 1e16;

// a^n (mod.MOD)を求める。計算量はO(logn)
ll modpow(ll a, ll n, ll MOD = mod) {
    if(n == 0) {
        return 1;
    }
    if(n%2 == 1) {
        return (a * modpow(a, n-1, MOD)) % MOD;
    }
    return (modpow(a, n/2, MOD) * modpow(a, n/2, MOD)) % MOD;
}

// nCrをO(r)で求める。
ll Comb(ll n, ll r) {
    if(n < r) {
        return 0;
    }
    if(r > n-r) {
        return Comb(n, n-r);
    }
    ll Mul = 1, Div = 1;
    rep(i, r) {
        Mul *= (n-i);  Div *= (i+1);
        Mul %= mod;  Div %= mod;
    }
    return Mul * modpow(Div, mod - 2) % mod; 
}

int main() {
    ll n, m;
    cin >> n >> m;

    ll s = 0;
    rep(i, n) {
        ll a;
        cin >> a;
        s += a;
    }

    out(Comb(n+m, n+s));
    re0;
}
/*
Written By mafailure
*/
#define ill
//In the name of God
#include<bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp> // Common file 
#include <ext/pb_ds/tree_policy.hpp> 
#include <functional> // for less
using namespace std;
using namespace __gnu_pbds;
#define IOS ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define endl "\n"
#ifdef ill
#define int long long 
#endif
template<typename T> ostream& operator<<(ostream &os, const vector<T> &v) { os << '{'; string sep; for (const auto &x : v) os << sep << x, sep = ", "; return os << '}'; }
template<typename T, size_t size> ostream& operator<<(ostream &os, const array<T, size> &arr) { os << '{'; string sep; for (const auto &x : arr) os << sep << x, sep = ", "; return os << '}'; }
template<typename A, typename B> ostream& operator<<(ostream &os, const pair<A, B> &p) { return os << '(' << p.first << ", " << p.second << ')'; }

void dbg_out() { cerr << endl; }
template<typename Head, typename... Tail> void dbg_out(Head H, Tail... T) { cerr << ' ' << H; dbg_out(T...); }
 
#ifdef AATIF_DEBUG
#define dbg(...) cerr << "(" << #__VA_ARGS__ << "):", dbg_out(__VA_ARGS__)
#else
#define dbg(...)
#endif
//#define int long long 
// int dx[]={-1,1,0,0}; int dy[]={0,0,1,-1};
// int dx[]={2,2,-2,-2,1,1,-1,-1}; int dy[]={1,-1,1,-1,2,-2,2,-2};
const long long mod = 1e9 + 7;
const double eps=1e-9;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<string> vs;
typedef vector<bool> vb;
typedef pair<int, int> ii;
typedef vector< pair< int, int > > vii;
typedef map<int, int> mii;
typedef pair<int, ii> pip;
typedef pair<ii, int> ppi;
#define arrinp(arr,init,final,size,type) type* arr=new type[size];for(int i=init;i<final;i++)cin>>arr[i];
#define cr2d(arr,n,m,t) t**arr=new t*[n];for(int i=0;i<n;i++)arr[i]=new t[m];
#define w(t) int t;cin>>t; while(t--)
#define takeInp(n) int n;cin>>n;
#define fr(i,init,final) for(int i=init;i<final;i++)
#define frr(i,init,final) for(int i=init;i>=final;i--)
#define Fr(i,final) for(int i=0;i<final;i++)
#define Frr(i,first) for(int i=first;i>=0;i--)
#define fi first
#define se second
#define mp make_pair
#define pb push_back
#define all(c) (c).begin(),(c).end()
#define rall(c) (c).rbegin(),(c).rend()
#define debug(x) cerr<<">value ("<<#x<<") : "<<x<<endl;
#define setb __builtin_popcount
#define lsone(n) (n&(-n))
#define rlsone(n) (n&(n-1))
#define clr(a,b) memset(a,b,sizeof(a))
const int inf= INT_MAX;
//struct point_i{int x,y;};
struct point_i{int x,y;
point_i(){ x=0; y=0;}
point_i(int x_,int y_){x=(x_);y=(y_) ;}
};

struct point 
{
	float x,y;
	point (){x=y=0.0;}
	point (float x_,float y_){x=(x_); y=(y_);}
	bool operator < (point other) const{
	  if(fabs(x-other.x)>eps)return x<other.x;
	  return y<other.y;
		
		}
	bool operator == (point other) const {
		return fabs(other.x-x)<=eps&& fabs(other.y-y)<=eps;
		}
	
} ;
typedef tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update>  ordered_set; 
vi init(string s)
{
	istringstream sin(s);
	int n;
	vi arr;
	while(sin>>n)arr.push_back(n);
	return arr;
}
int power(int x, int y)
{ 
	if(y==0)return 1;
	int u=power(x,y/2);
	u=(u*u)%mod;
	if(y%2)u=(x*u)%mod;
	return u;
    
}
int gcd(int a,int b)
{
	if(a<b)return gcd(b,a);
	return (b==0?a:(a%b?gcd(b,a%b):b));
}
int gcd_e(int a,int b,int &x,int &y)
{
	
	if(b==0){x=1; y=0; return a;}
	int x1,y1;
	int p=gcd_e(b,a%b,x1,y1);
	x=y1;
	y=x1-(a/b)*y1;
	return p;
}

int mul(int a,int b)
{
	return (a*b)%mod; 
}
int inv(int n)
{
	return power(n,mod-2);
}

signed main()
{
	IOS
	int n; cin>>n; 
	int m; cin>>m; 
	
	vi a(n);             
	fr(i,0,n) cin>>a[i];
	int sum=accumulate(all(a),n); 
	int num=1; 
	int den=1; 
	m+=n;
	fr(i,0,sum)
	{
		num=mul(num,m-i); 
		den=mul(den,sum-i);
	}
	cout<<mul(num,inv(den))<<endl;
	//fr(i,0,n) sum+=a[i]; 
	
	
	
	 
	
	
}
