#include<cstdio>
#include<algorithm>
#include<vector>
#define SZ 262144
using namespace std;
int n, M, A[2010];
long long Mod = 1000000007, Inv[101000];

long long Pow(long long a, long long b){
    long long r=1;
    while(b){
        if(b&1)r=r*a%Mod;
        a=a*a%Mod;b>>=1;
    }
    return r;
}

long long Comb(int a, int b){
    int i;
    long long r=1;
    for(i=1;i<=b;i++){
        r=r*(a-i+1)%Mod;
        r=r*Pow(i,Mod-2)%Mod;
    }
    return r;
}

int main(){
    int i;
    for(i=1;i<=100000;i++)Inv[i]=Pow(i,Mod-2);
    scanf("%d%d",&n,&M);
    long long r=1;
    int H = 0, s = 0;
    for(i=1;i<=n;i++){
        scanf("%d",&A[i]);
        H+=A[i]+1;
        s+=A[i];
    }
    if(s>M){
        puts("0");
        return 0;
    }
    printf("%lld\n",Comb(H+M-s, H));
}
// atcoder/abc185/E/main.cpp
// author: @___Johniel
// github: https://github.com/johniel/

#include <bits/stdc++.h>

#define each(i, c) for (auto& i : c)
#define unless(cond) if (!(cond))

using namespace std;

template<typename P, typename Q> ostream& operator << (ostream& os, pair<P, Q> p) { os << "(" << p.first << "," << p.second << ")"; return os; }
template<typename P, typename Q> istream& operator >> (istream& is, pair<P, Q>& p) { is >> p.first >> p.second; return is; }
template<typename T> ostream& operator << (ostream& os, vector<T> v) { os << "("; for (auto& i: v) os << i << ","; os << ")"; return os; }
template<typename T> istream& operator >> (istream& is, vector<T>& v) { for (auto& i: v) is >> i; return is; }
template<typename T> ostream& operator << (ostream& os, set<T> s) { os << "#{"; for (auto& i: s) os << i << ","; os << "}"; return os; }
template<typename K, typename V> ostream& operator << (ostream& os, map<K, V> m) { os << "{"; for (auto& i: m) os << i << ","; os << "}"; return os; }

template<typename T> inline T setmax(T& a, T b) { return a = std::max(a, b); }
template<typename T> inline T setmin(T& a, T b) { return a = std::min(a, b); }

using lli = long long int;
using ull = unsigned long long;
using point = complex<double>;
using str = string;
template<typename T> using vec = vector<T>;

constexpr array<int, 8> di({0, 1, -1, 0, 1, -1, 1, -1});
constexpr array<int, 8> dj({1, 0, 0, -1, 1, -1, -1, 1});
constexpr lli mod = 1e9 + 7;

int main(int argc, char *argv[])
{
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.setf(ios_base::fixed);
  cout.precision(15);

  int n, m;
  while (cin >> n >> m) {
    vec<int> a(n);
    vec<int> b(m);
    cin >> a >> b;
    const int N = 1000 + 3;
    static int dp[N][N];
    const int inf = 1 << 29;
    fill(&dp[0][0], &dp[N - 1][N - 1] + 1, inf);
    dp[0][0] = 0;
    for (int i = 0; i <= n; ++i) {
      for (int j = 0; j <= m; ++j) {
        if (i < n && j < m) {
          if (a[i] == b[j]) {
            setmin(dp[i + 1][j + 1], dp[i][j]);
          } else {
            setmin(dp[i + 1][j + 1], dp[i][j] + 1);
          }
        }
        if (j < m) setmin(dp[i][j + 1], dp[i][j] + 1);
        if (i < n) setmin(dp[i + 1][j], dp[i][j] + 1);
      }
    }
    cout << dp[n][m] << endl;
  }

  return 0;
}
