#include<bits/stdc++.h>
using namespace std;
#define all(x) (x).begin(), (x).end()
#define sz(x) ( (int)(x).size() )
using LL = long long;
const int mod = 1e9 + 7;
mt19937 rng( (uint32_t)chrono::steady_clock::now().time_since_epoch().count() );
struct Mint {
int a;
Mint(int _a = 0) : a(_a) {}
friend ostream& operator << (ostream &out, const Mint &_) {
out << _.a;
return out;
}
bool operator == (const Mint &_) const { return a == _.a; }
bool operator ! () const { return !a; }
Mint operator + (const Mint &_) const {
int ret = a + _.a;
return ret < mod ? Mint(ret) : Mint(ret - mod);
}
Mint operator - (const Mint &_) const { return *this + Mint(mod - _.a); }
Mint operator * (const Mint &_) const { return Mint( (int)( (LL)a * _.a % mod) ); }
friend Mint& operator += (Mint &a, const Mint &b) { return a = a + b; }
friend Mint& operator -= (Mint &a, const Mint &b) { return a = a - b; }
friend Mint& operator *= (Mint &a, const Mint &b) { return a = a * b; }
Mint& operator ++ () { return *this = *this + Mint(1); }
Mint& operator -- () { return *this = *this - Mint(1); }
template<class T> Mint binPow(T exp) const {
Mint ret(1), c = *this;
for (; exp; exp >>= 1, c *= c) if (exp & 1) ret *= c;
return ret;
}
};
vector<Mint> fact, invFact;
Mint binomial(int n, int k) { return fact[n] * invFact[k] * invFact[n - k]; }
int main() {
ios_base::sync_with_stdio(0); cin.tie(0);
#ifdef FourLeafClover
freopen("input", "r", stdin);
#endif // FourLeafCLover
int n, k; cin >> n >> k;
fact.assign(n + 2, Mint() );
fact[0] = Mint(1); for (int i = 1; i < sz(fact); ++i) fact[i] = fact[i - 1] * Mint(i);
invFact.assign(sz(fact), Mint() );
invFact.back() = fact.back().binPow<int>(mod - 2);
for (int i = sz(invFact) - 2; i >= 0; --i) invFact[i] = invFact[i + 1] * Mint(i + 1);
Mint ans;
for (int i = 0; i < k; ++i) {
if (i & 1) ans -= binomial(n + 1, i) * Mint(k - i).binPow<int>(n);
else ans += binomial(n + 1, i) * Mint(k - i).binPow<int>(n);
}
cout << ans << '\n';
return 0;
}
