#include <bits/stdc++.h>

using namespace std;

typedef long long i64;
typedef unsigned long long ui64;
typedef vector<i64> vi;
typedef vector<vi> vvi;
typedef pair<i64, i64> pi;

#define pb push_back
#define sz(a) i64((a).size())
#define all(c) (c).begin(), (c).end()
#define REP(s, e, i) for(i=(s); i < (e); ++i)
inline void RI(i64 &i) {scanf("%lld", &(i));}
inline void RVI(vi &v) { for(i64 i=0;i<sz(v);++i) { RI(v[i]); } }
inline void RVVI(vvi &vv) { for(i64 i=0;i<sz(vv);++i) { RVI(vv[i]); } }
inline void WI(const i64 &i) {printf("%lld\n", i);}
inline void WVI(const vi &v, char sep=' ') { for(i64 i=0;i<sz(v);++i) { if(i != 0){ printf("%c", sep); } printf("%lld", v[i]);} printf("\n"); }
inline void WS(const string &s) { printf("%s\n", s.c_str()); }
inline void WB(bool b, const string &yes, const string &no) { if(b){ WS(yes);} else { WS(no);} }
inline void YESNO(bool b) { WB(b, "YES", "NO"); }
inline void YesNo(bool b) { WB(b, "Yes", "No"); }
#define BUF_LENGTH 1000000
inline void RS(string &s) {static char buf[BUF_LENGTH]; scanf("%s", buf); s = buf;}
template<typename T> inline bool IN(T &S, const typename T::key_type &key) {
  return S.find(key) != S.end();
}
template<typename T> inline bool ON(const T &b, i64 idx) {
  return ((T(1) << idx) & b) != 0;
}

template<long long M, typename T=long long>
struct modint {
  modint(T v=T(0)) : val((v >= 0 ? v : (M - ((-v) % M))) % M) {}
  using this_type = modint<M, T>;
  T val;
  this_type operator++(int) {
    this_type ret = *this;
    val++; val %= M;
    return ret;
  }
  this_type operator--(int) {
    this_type ret = *this;
    val += M-1; val %= M;
    return ret;
  }
  this_type &operator++() {
    val++; val %= M;
    return *this;
  }
  this_type &operator--() {
    val += M-1; val %= M;
    return *this;
  }
  this_type operator+() const { return *this; }
  this_type operator-() const { return this_type(M-val); };
  friend this_type operator+(const this_type &lhs, const this_type &rhs) {
    return this_type(lhs) += rhs;
  }
  friend this_type operator-(const this_type &lhs, const this_type &rhs) {
    return this_type(lhs) -= rhs;
  }
  friend this_type operator*(const this_type &lhs, const this_type &rhs) {
    return this_type(lhs) *= rhs;
  }
  friend this_type operator/(const this_type &lhs, const this_type &rhs) {
    return this_type(lhs) /= rhs;
  }
  this_type pow(long long b) const {
    this_type ret = 1, a = *this;    
    while(b != 0) {
      if(b % 2 != 0) {
        ret *= a;
      }
      b /= 2;
      a = a * a;
    }
    return ret;
  }
  this_type inv() const {
    return pow(M-2);
  }
  this_type& operator+=(const this_type &rhs) {
    val += rhs.val; val %= M; return *this;
  }
  this_type& operator-=(const this_type &rhs) {
    val += M - rhs.val; val %= M; return *this;
  }
  this_type& operator*=(const this_type &rhs) {
    val *= rhs.val; val %= M; return *this;
  }
  this_type& operator/=(const this_type &rhs) {
    *this *= rhs.inv(); return *this;
  }
  friend bool operator==(const this_type &lhs, const this_type &rhs) {
    return lhs.val == rhs.val;
  }
  friend bool operator!=(const this_type &lhs, const this_type &rhs) {
    return lhs.val != rhs.val;
  }
  T mod() const {return M;}
};

using mi = modint<1000000007>;
using vmi = vector<mi>;
using vvmi = vector<vmi>;

int main(int argc, char *argv[]) {
  i64 i, j, k;  
  i64 N, M; cin >> N >> M;
  vi A(N); RVI(A);
  i64 S = accumulate(all(A), 0LL);
  mi ans = 1;
  REP(0, S+N, i) {
    ans *= (N + M - i);
    ans /= i + 1;
  }
  WI(ans.val);

  return 0;
}


#include<bits/stdc++.h>
using namespace std;
const int mod=1e9+7;
const int N=3e5+5;
int n,m,k,cnt,tot,cas,ans;
int a[N];
bool vis[N];
char s[N];
#define ll long long
long long qmi(long long a,long long b)
{
	long long ans=1;
	while(b){
		if(b&1) ans=ans*a%mod;
		b>>=1;a=a*a%mod;
	}
	return ans;
}
ll C(ll n,ll r)
{
	if(r>n||r<0) return 0;
	ll fz=1,fm=1;
	for(int i=1;i<=r;i++)
		fz=fz*(n-i+1)%mod,fm=fm*i%mod;
	return fz*qmi(fm,mod-2)%mod; 
}
int main()
{
	long long sum=0;
	cin>>n>>m;
	for(int i=1;i<=n;i++)
		cin>>a[i],sum+=a[i];
	printf("%lld\n",C(n+m,sum+n));
	return 0;
}