import scala.collection.mutable.* import scala.io.StdIn.* import scala.util.chaining.* import scala.math.* import scala.reflect.ClassTag import scala.util.* import scala.annotation.tailrec import scala.collection.mutable object ModInt: opaque type ModInt = Long inline def zero: ModInt = 0 inline def one: ModInt = 1 extension (value: Long) inline def toModInt(using inline mod: Int): ModInt = value % mod inline def unsafeAsModInt: ModInt = value extension (value: Int) inline def toModInt(using inline mod: Int): ModInt = value % mod inline def unsafeAsModInt: ModInt = value trait Converter[T]: inline def convert(value: T)(using inline mod: Int): ModInt inline given Converter[Int] with override inline def convert(value: Int)(using inline mod: Int) = value.toModInt inline given Converter[Long] with override inline def convert(value: Long)(using inline mod: Int) = value.toModInt inline given Converter[ModInt] with override inline def convert(value: ModInt)(using inline mod: Int) = value extension (modInt: ModInt) inline def value(using inline mod: Int): Long = (modInt + mod) % mod inline def rawValue: Long = modInt inline def inverse(using inline mod: Int): ModInt = var x = modInt var y = mod.toLong var a = 1L var b = 0L var c = 0L var d = 1L while y != 0 do val q = x / y val e = a - c * q val f = b - d * q a = c b = d c = e d = f x = y y = c * modInt + d * mod require(x.abs == 1L) if x == 1 then a % mod else -a % mod inline def pow(exp: Long)(using inline mod: Int): ModInt = var result = 1L var base = modInt var e = exp while e > 0 do if (e & 1) == 1 then result = result * base % mod base = base * base % mod e >>= 1 result inline def pow(exp: Int)(using inline mod: Int): ModInt = pow(exp.toLong) extension [L: Converter, R: Converter] (left: L) inline def +(right: R)(using inline mod: Int): ModInt = (summon[Converter[L]].convert(left) + summon[Converter[R]].convert(right)).toModInt inline def -(right: R)(using inline mod: Int): ModInt = (summon[Converter[L]].convert(left) - summon[Converter[R]].convert(right)).toModInt inline def *(right: R)(using inline mod: Int): ModInt = (summon[Converter[L]].convert(left) * summon[Converter[R]].convert(right)).toModInt inline def /(right: R)(using inline mod: Int): ModInt = (summon[Converter[L]].convert(left) * summon[Converter[R]].convert(right).inverse).toModInt inline def powMod(base: Long, exp: Long)(using inline mod: Int): ModInt = base.toModInt.pow(exp) inline given mod: Int = 1000000007 import ModInt.* @main def main = val Array(height, width) = readLine.split(' ').map(_.toInt) val factorial = Array.fill(max(height, width) + 1){one} for i <- 2 until factorial.length do factorial(i) = i * factorial(i - 1) val inverse = Array.fill(factorial.length){one}.tap(_(factorial.length - 1) = factorial.last.inverse) for i <- inverse.length - 1 until 2 by -1 do inverse(i - 1) = i * inverse(i) def combination(n: Int, r: Int): ModInt = factorial(n) * inverse(r) * inverse(n - r) var result = zero for i <- 0 to height do val value = combination(height, i) * (1 - powMod(2, height - i)).pow(width) if (i + width) % 2 == 0 then result += value else result -= value println(result.value)