#include <iostream>
#include <vector>
#include <cassert>
#define repeat(i,n) for (int i = 0; (i) < (n); ++(i))
typedef long long ll;
using namespace std;
ll powi(ll x, ll y, ll p) { // O(log y)
    assert (y >= 0);
    x = (x % p + p) % p;
    ll z = 1;
    for (ll i = 1; i <= y; i <<= 1) {
        if (y & i) z = z * x % p;
        x = x * x % p;
    }
    return z;
}
ll inv(ll x, ll p) { // p must be a prime, O(log p)
    assert ((x % p + p) % p != 0);
    return powi(x, p-2, p);
}

template <typename T, typename F>
T powt(T x, ll y, T unit, F f) {
    T z = unit;
    for (ll i = 1; i <= y; i <<= 1) {
        if (y & i) z = f(z, x);
        x = f(x, x);
    }
    return z;
}
const int mod = 1e9+7;
vector<vector<ll> > operator * (vector<vector<ll> > const & p, vector<vector<ll> > const & q) {
    int n = p.size();
    vector<vector<ll> > r(n, vector<ll>(n));
    repeat (y,n) {
        repeat (z,n) {
            repeat (x,n) {
                r[y][x] += p[y][z] * q[z][x] % mod;
                r[y][x] %= mod;
            }
        }
    }
    return r;
}
vector<ll> operator * (vector<vector<ll> > const & p, vector<ll> const & q) {
    int n = p.size();
    vector<ll> r(n);
    repeat (y,n) {
        repeat (z,n) {
            r[y] += p[y][z] * q[z] % mod;
            r[y] %= mod;
        }
    }
    return r;
}
vector<vector<ll> > unit_matrix(int n) {
    vector<vector<ll> > e(n, vector<ll>(n));
    repeat (i,n) e[i][i] = 1;
    return e;
}
vector<vector<ll> > zero_matrix(int n) {
    vector<vector<ll> > o(n, vector<ll>(n));
    return o;
}
vector<vector<ll> > powm(vector<vector<ll> > const & f, ll k) {
    int n = f.size();
    return powt(f, k, unit_matrix(n), [&](vector<vector<ll> > const & a, vector<vector<ll> > const & b) { return a * b; });
}
int main() {
    int n; ll c; cin >> n >> c;
    vector<int> a(n); repeat (i,n) cin >> a[i];
    vector<vector<ll> > f = zero_matrix(n);
    repeat (y,n) repeat (x,y+1) f[y][x] = a[x];
    vector<ll> x(n, 1);
    vector<ll> y = powm(f, c) * x;
    ll ans = y[n-1];
    repeat (i,n) ans = (ans - powi(a[i], c, mod) + mod) % mod;
    cout << ans << endl;
    return 0;
}