import java.io.BufferedReader
import java.io.InputStream
import java.io.InputStreamReader
import java.io.PrintWriter
import java.lang.StringBuilder
import java.util.*

fun PrintWriter.solve(sc: FastScanner) {
    val n = sc.nextInt()
    val k = sc.nextInt()
    if(!(n in 1..100000 && k in 1..1000000000)) {
        throw IllegalArgumentException()
    }
    val dp = Array(n) { 1L }
    val mod = 1000000007L
    for (i in 1 until n) {
        dp[i] = dp[i - 1] + if (i >= k) dp[i - k] else 0
        dp[i] %= mod
    }
    println(dp[n - 1])
}

fun main(args: Array<String>) {
    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()
}