import java.io.InputStream import java.io.PrintWriter import java.util.* // ModInt // region class ModInt(x: Long) { companion object { const val MOD = 1000000007L //const val MOD = 998244353L } val x = (x % MOD + MOD) % MOD operator fun plus(other: ModInt): ModInt { return ModInt(x + other.x) } operator fun minus(other: ModInt): ModInt { return ModInt(x - other.x) } operator fun times(other: ModInt): ModInt { return ModInt(x * other.x) } operator fun div(other: ModInt): ModInt { return this * other.inv() } fun pow(exp: Long): ModInt { if (exp == 0L) return ModInt(1L) var a = pow(exp shr 1) a *= a if (exp and 1L == 0L) return a return this * a } fun inv(): ModInt { return this.pow(MOD - 2) } override fun equals(other: Any?): Boolean { if (this === other) return true if (javaClass != other?.javaClass) return false other as ModInt if (x != other.x) return false return true } override fun hashCode(): Int { return x.hashCode() } override fun toString(): String { return "$x" } } val fac = mutableListOf() val invfac = mutableListOf() fun fact(n: Long, b: Boolean): ModInt { if (fac.count() == 0) { fac.add(ModInt(1)) invfac.add(ModInt(1)) } while (fac.count() <= n) { fac.add(fac.last() * ModInt(fac.count().toLong())) invfac.add(fac.last().inv()) } return if (b) { fac[n.toInt()] } else { invfac[n.toInt()] } } fun comb(n: Long, k: Long): ModInt { return fact(n, true) * fact(k, false) * fact(n - k, false) } fun comb2(n: Long, k: Long): ModInt { var ans = ModInt(1) for (i in 0 until k) { ans = ans * ModInt(n - i) / ModInt(k - i) } return ans } // endregion fun PrintWriter.solve() = with(FastScanner(System.`in`)) { val n = nextLong() val k = nextLong() val a = ModInt(k) * ModInt(k + 3) / ModInt(2) val b = ModInt(k) * ModInt(k + 1) / ModInt(2) println(a.pow(n) - b.pow(n)) } fun main() { val writer = PrintWriter(System.out, false) writer.solve() writer.flush() } class FastScanner(s: InputStream) { private var st = StringTokenizer("") private val br = s.bufferedReader() fun next(): String { while (!st.hasMoreTokens()) st = StringTokenizer(br.readLine()) return st.nextToken() } fun nextInt() = next().toInt() fun nextLong() = next().toLong() fun nextLine() = br.readLine() fun nextDouble() = next().toDouble() }