#include //typedef //-------------------------#include const double pi = 3.141592653589793238462643383279; using namespace std; //conversion //------------------------------------------ inline int toInt(string s) { int v; istringstream sin(s); sin >> v; return v; } template inline string toString(T x) { ostringstream sout; sout << x; return sout.str(); } inline int readInt() { int x; scanf("%d", &x); return x; } //typedef //------------------------------------------ typedef vector VI; typedef vector VVI; typedef vector VS; typedef pair PII; typedef pair PLL; typedef pair TIII; typedef long long LL; typedef unsigned long long ULL; typedef vector VLL; typedef vector VVLL; //container util //------------------------------------------ #define ALL(a) (a).begin(), (a).end() #define RALL(a) (a).rbegin(), (a).rend() #define PB push_back #define MP make_pair #define SZ(a) int((a).size()) #define SQ(a) ((a) * (a)) #define EACH(i, c) for (typeof((c).begin()) i = (c).begin(); i != (c).end(); ++i) #define EXIST(s, e) ((s).find(e) != (s).end()) #define SORT(c) sort((c).begin(), (c).end()) //repetition //------------------------------------------ #define FOR(i, s, n) for (int i = s; i < (int)n; ++i) #define REP(i, n) FOR(i, 0, n) #define MOD 1000000007 #define rep(i, a, b) for (int i = a; i < (b); ++i) #define trav(a, x) for (auto &a : x) #define all(x) x.begin(), x.end() #define sz(x) (int)(x).size() typedef long long ll; typedef pair P; typedef pair pii; typedef vector vi; const double EPS = 1E-8; #define chmin(x, y) x = min(x, y) #define chmax(x, y) x = max(x, y) class UnionFind { public: vector par; vector siz; UnionFind(int sz_) : par(sz_), siz(sz_, 1) { for (ll i = 0; i < sz_; ++i) par[i] = i; } void init(int sz_) { par.resize(sz_); siz.assign(sz_, 1LL); for (ll i = 0; i < sz_; ++i) par[i] = i; } int root(int x) { if (par[x] == x) { return x; } else { return par[x] = root(par[x]); } } bool merge(int x, int y) { x = root(x); y = root(y); if (x == y) return false; if (siz[x] < siz[y]) swap(x, y); siz[x] += siz[y]; par[y] = x; return true; } bool issame(int x, int y) { return root(x) == root(y); } int size(int x) { return siz[root(x)]; } }; ll modPow(ll x, ll n, ll mod = MOD) { if (n == 0) return 1; ll res = 1; while (n) { if (n & 1) res = (res * x) % mod; res %= mod; x = x * x % mod; n >>= 1; } return res; } #define SIEVE_SIZE 5000000 + 10 bool sieve[SIEVE_SIZE]; void makeSieve() { for (int i = 0; i < SIEVE_SIZE; ++i) sieve[i] = true; sieve[0] = sieve[1] = false; for (int i = 2; i * i < SIEVE_SIZE; ++i) if (sieve[i]) for (int j = 2; i * j < SIEVE_SIZE; ++j) sieve[i * j] = false; } bool isprime(ll n) { if (n == 0 || n == 1) return false; for (ll i = 2; i * i <= n; ++i) if (n % i == 0) return false; return true; } const int MAX = 200010; long long fac[MAX], finv[MAX], inv[MAX]; const ll mod2 = 998244353; const ll mod3 = 1777777777; // テーブルを作る前処理 void COMinit() { fac[0] = fac[1] = 1; finv[0] = finv[1] = 1; inv[1] = 1; for (ll i = 2; i < MAX; i++) { fac[i] = fac[i - 1] * i % MOD; inv[i] = MOD - inv[MOD % i] * (MOD / i) % MOD; finv[i] = finv[i - 1] * inv[i] % MOD; //cout << fac[i] << " " << inv[i] << " " << finv[i] << endl; } } // 二項係数計算 long long COM(int n, int k) { if (n < k) return 0; if (n < 0 || k < 0) return 0; return fac[n] * (finv[k] * finv[n - k] % MOD) % MOD; } long long extGCD(long long a, long long b, long long &x, long long &y) { if (b == 0) { x = 1; y = 0; return a; } long long d = extGCD(b, a % b, y, x); y -= a / b * x; return d; } // 負の数にも対応した mod (a = -11 とかでも OK) inline long long mod(long long a, long long m) { return (a % m + m) % m; } // 逆元計算 (ここでは a と m が互いに素であることが必要) long long modinv(long long a, long long m) { long long x, y; extGCD(a, m, x, y); return mod(x, m); // 気持ち的には x % m だが、x が負かもしれないので } ll GCD(ll a, ll b) { if (b == 0) return a; return GCD(b, a % b); } typedef vector vec; typedef vector mat; mat mul(mat &A, mat &B) { mat C(A.size(), vec((int)B[0].size())); for (int i = 0; i < A.size(); ++i) { for (int k = 0; k < B.size(); ++k) { for (int j = 0; j < B[0].size(); ++j) { C[i][j] = (C[i][j] + A[i][k] % MOD * B[k][j] % MOD) % MOD; } } } return C; } mat matPow(mat A, ll n) { mat B(A.size(), vec((int)A.size())); for (int i = 0; i < A.size(); ++i) { B[i][i] = 1; } while (n > 0) { if (n & 1) B = mul(B, A); A = mul(A, A); n >>= 1; } return B; } template struct Fenwick { int N; vector bit; Fenwick() : N(0) {} Fenwick(int n) : N(n), bit(n + 1, 0) {} void add(int i, ll x) { //0-indexedを避けるために加算 while (i <= N) { bit[i] += x; i += (i & -i); } } ll sum(int i) { ll res = 0; while (i > 0) { res += bit[i]; i -= (i & -i); } return res; } ll range(int i, int j) { return sum(j) - sum(i); } ll get(int i) { return sum(i) - sum(i - 1); } ll getKth(ll k) { ++k; int res = 0; int n = 1; while (n < bit.size()) n *= 2; for (int i = n / 2; i > 0; i /= 2) { if (res + i < bit.size() && bit[res + i] < k) { k = k - bit[res + i]; res = res + i; } } return res + 1; } // bitは1-indexedで実装しているのでバグった時は初めに確認すること }; int main() { cin.tie(0); ios::sync_with_stdio(false); cout << fixed << setprecision(4); ll N, K; cin >> N >> K; ll ans = 0; COMinit(); for (int i = 0; i <= K; i++) { ll c = 1; if ((K - i) % 2 == 1) { c *= -1; } ans += c * COM(K, i) * modPow(i, N, MOD); ans = (ans + MOD) % MOD; } cout << ans << endl; return 0; }