import java.io.BufferedReader import java.io.InputStream import java.io.InputStreamReader import java.io.PrintWriter import java.lang.StringBuilder import java.util.* // region class ModInt(x: Long) { companion object { const val MOD = 1e9.toLong() + 7 } 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() fun fact(n: Long): ModInt { if (fac.count() == 0) fac.add(ModInt(1)) while (fac.count() <= n) { fac.add(fac.last() * ModInt(fac.count().toLong())) } return fac[n.toInt()] } fun comb(n: Long, k: Long): ModInt { return fact(n) / fact(k) / fact(n - k) } 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(sc: FastScanner) { val n = sc.nextInt() val k = sc.nextInt() var ans = ModInt(0) var i = 0 while (n - i * k >= 0) { ans += comb((n - i * k + i).toLong(), i.toLong()) i++ } println(ans) } fun main(args: Array) { val writer = PrintWriter(System.out, false) writer.solve(FastScanner(System.`in`)) writer.flush() } class FastScanner(s: InputStream) { private var st = StringTokenizer("") private val br = BufferedReader(InputStreamReader(s)) 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() fun ready() = br.ready() }