//author:
#include <bits/stdc++.h>
using namespace std;
using i64 = long long;
#define ONLINE_JUDGE
const int MOD = 1e9 + 7;
int fak[10000 + 5];
int fp(int a, int b) {
int res = 1;
while(b) {
if(b & 1) {
res = (1LL * res * a) % MOD;
}
a = (1LL * a * a) % MOD;
b >>= 1;
}
return res;
}
int divide(int a) {
return fp(a, MOD -2);
}
int divide(int a, int b) {
return (1LL * a * divide(b)) % MOD;
}
int comb(int n, int r) {
if(n < r)
return 0;
return divide(fak[n], (1LL * fak[r] * fak[n - r]) % MOD);
}
void solve() {
int n, l;
cin >> n >> l;
vector <int> vec(n);
for(int &i : vec)
cin >> i;
int parca = l - ((n -1) * (vec[0] -1));
cout << (1LL * comb(parca, n) * fak[n]) % MOD;
return;
}
signed main() {
#ifndef ONLINE_JUDGE
freopen(".in", "r", stdin);
freopen(".out", "w", stdout);
#endif
fak[0] = 1;
for(int i = 1; i <= 10000; i++)
fak[i] = (1LL * fak[i -1] * i) % MOD;
ios_base::sync_with_stdio(false);
cin.tie(NULL); cout.tie(NULL);
int t = 1; //cin >> t;
while(t--)
solve();
return 0;
}
