#include <bits/stdc++.h>
using namespace std;
#define ll long long
const ll mod = 1e9 + 7;
const ll DIM = 1e5 + 7;
ll a[DIM], p[DIM];
ll C(ll n, ll k) {
ll ans = 1;
for (int i=1; i<=k; i++) {
ans = ans * (n-k + i) / i;
ans %= mod;
}
return ans;
}
int main(){
ios::sync_with_stdio(false);cin.tie(nullptr); cout.tie(nullptr);
ll n, L;
cin >> n >> L;
ll r;
for (int i=1; i<=n; i++) {
cin >> r;
}
ll answer = 0;
for (int i=n+(n-1)*(r-1); i<=L; i++) {
answer += C(i - n - (n-1)*(r-1) + n-1 - 1, n-2);
answer %= mod;
}
for (int i=1; i<=n; i++) {
answer *= i;
answer %= mod;
}
cout << answer << endl;
}
;
