#include #include #include #include template struct Factorial { int n; std::vector fact; std::vector revfact; Factorial(int n) : n(n) { fact.resize(n + 1); revfact.resize(n + 1); fact[0] = 1; for (int i = 0; i < n; ++i) fact[i + 1] = fact[i] * (i + 1); revfact[n] = fact[n].inv(); for (int i = n - 1; i >= 0; --i) revfact[i] = revfact[i + 1] * (i + 1); } T comb(int n, int r) { if (n < r || r < 0) return 0; return fact[n] * revfact[r] * revfact[n - r]; } T perm(int n, int r) { if (n < r || r < 0) return 0; return fact[n] * revfact[n - r]; } }; #include #include #include template bool chmax(T &a, const T &b) { if (a < b) { a = b; return true; } return false; } template bool chmin(T &a, const T &b) { if (a > b) { a = b; return true; } return false; } template T div_floor(T a, T b) { if (b < 0) a *= -1, b *= -1; return a >= 0 ? a / b : (a + 1) / b - 1; } template T div_ceil(T a, T b) { if (b < 0) a *= -1, b *= -1; return a > 0 ? (a - 1) / b + 1 : a / b; } template struct CoordComp { std::vector v; bool sorted; CoordComp() : sorted(false) {} int size() { return v.size(); } void add(T x) { v.push_back(x); } void build() { std::sort(v.begin(), v.end()); v.erase(std::unique(v.begin(), v.end()), v.end()); sorted = true; } int get_idx(T x) { assert(sorted); return lower_bound(v.begin(), v.end(), x) - v.begin(); } T &operator[](int i) { return v[i]; } }; #define For(i, a, b) for (int i = (int)(a); (i) < (int)(b); ++(i)) #define rFor(i, a, b) for (int i = (int)(a)-1; (i) >= (int)(b); --(i)) #define rep(i, n) For(i, 0, n) #define rrep(i, n) rFor(i, n, 0) #define fi first #define se second using namespace std; using lint = long long; using pii = pair; using pll = pair; using mint = atcoder::modint1000000007; int main() { int h, w; scanf("%d%d", &h, &w); Factorial fc(h); mint ans = (mint(2).pow(h) - 1).pow(w); For(i, 1, h) { mint tmp = fc.comb(h, i) * (mint(2).pow(h - i) - 1).pow(w); if (i % 2 == 1) ans -= tmp; else ans += tmp; } printf("%u\n", ans.val()); }