import java.io.*
import java.util.*
import java.lang.*
import java.lang.Math.*

class LongMod(var num: Long, val MOD: Long = 1_000_000_007L) {
    init {
        this.num = (this.num%this.MOD + this.MOD)%this.MOD
    }
    constructor(numStr: String, MOD: Long = 1e9.toLong()+7) :
            this(0L, MOD) {
        if (numStr.isEmpty()) return
        var rv = numStr.reversed()
        var d = 1L
        rv.forEach{ c ->
            this.num += (c - '0') * d
            this.num %= MOD
            d *= 10
            d %= MOD
        }
    }
    override operator fun equals(other: Any?): Boolean {
        if (other !is LongMod) return false
        return this.num % this.MOD == other.num % this.MOD
    }
    operator fun unaryMinus(): LongMod {
        return LongMod(-this.num)
    }
    private operator fun plusAssign(other: LongMod): Unit {
        if ((this.num + other.num) >= this.MOD) {
            this.num -= this.MOD
        }
        this.num += other.num
    }
    private operator fun minusAssign(other: LongMod): Unit {
        if ((this.num + this.MOD - other.num) >= this.MOD) {
            this.num -= this.MOD
        }
        this.num += this.MOD - other.num
    }
    private operator fun timesAssign(other: LongMod): Unit {
        this.num *= other.num
        this.num %= this.MOD
    }
    operator fun plus(other: LongMod): LongMod {
        val res = LongMod(this.num, this.MOD)
        res += other
        return res
    }
    operator fun minus(other: LongMod): LongMod {
        val res = LongMod(this.num, this.MOD)
        res -= other
        return res
    }
    operator fun times(other: LongMod): LongMod {
        val res = LongMod(this.num, this.MOD)
        res *= other
        return res
    }
    fun pow(n: Long): LongMod {
        if (n == 0L) return LongMod(1L, this.MOD)
        var x = this.pow(n / 2)
        x.timesAssign(x)
        if (n % 2 == 1L) x.timesAssign(this)
        return x
    }
    fun inv(): LongMod {
        return this.pow(this.MOD - 2)
    }
    operator fun divAssign(other: LongMod): Unit {
        this *= other.inv()
    }
    operator fun div(other: LongMod): LongMod {
        val res = LongMod(this.num, this.MOD)
        res /= other
        return res
    }
}

class NckLongModTbl(val N: Long, val MOD: Long = 1_000_000_007L) {
    private val fact: Array<LongMod>
    private val iFact: Array<LongMod>
    init {
        val n = N.toInt()
        this.fact = Array(n+1){LongMod(0L, MOD)}
        this.iFact = Array(n+1){LongMod(0L, MOD)}
        this.fact[0] = LongMod(1L, MOD)
        for (i in 1..n) {
            this.fact[i] = this.fact[i-1] * LongMod(i.toLong(), MOD)
        }
        this.iFact[n] = this.fact[n].inv()
        for (i in n downTo 1) {
            this.iFact[i-1] = this.iFact[i] * LongMod(i.toLong(), MOD)
        }
    }
    fun nCkMod(N: Long, K: Long): LongMod {
        if (K < 0 || N < K) return LongMod(0L, MOD)
        val n = N.toInt(); val k = K.toInt()
        return this.fact[n] * this.iFact[k] * this.iFact[n-k]
    }
    fun mHkMod(M: Long, K: Long): LongMod {
        return nCkMod(M-1+K, K)
    }
}

fun solve() {
    val (N, K) = rd.readLongArray()

    val tbl = NckLongModTbl(2*N)

    var ans = LongMod(0L)
    for (m in 0 until N) {
        if (m > K) break
        // 移動する m 人を選ぶ
        val nCm = tbl.nCkMod(N, m)
        // m 人を n-m 部屋に振り分ける
        val n_mHn = tbl.mHkMod(N-m, m)
        ans += nCm * n_mHn
    }

    print(ans.num)
}


//val rd = debug.Reader("abc", "156", "e", "sample-3")
val rd = Reader()


fun main(args: Array<String>) {
    try {
        var exception: Throwable? = null
        val sth = Thread(null, SolveThread(), "solveThread", 128 * 1024 * 1024)
        sth.setUncaughtExceptionHandler { _, e -> exception = e }
        sth.start(); sth.join()
        if (exception != null) throw exception!!
    } catch (e: Exception) { throw e }
}
const val MOD = 1_000_000_007L; const val INF = Int.MAX_VALUE/2; const val LINF = Long.MAX_VALUE/2
const val EPS = 1e-9; fun DBLEQ(a: Double, b: Double): Boolean {return abs(a - b) < EPS}
data class IntPair(val first: Int, val second: Int)
data class To(val idx: Int, val cost: Long)
fun <T>edge(V: Int): Array<ArrayList<T>> { return Array(V){ArrayList<T>()} }
val errPrintln: (Any) -> Unit = { msg -> System.err.println(msg) }
fun rAssert(exp: Boolean, lazyMsg: () -> String = {""}) {
    if (!exp) { val msg = lazyMsg(); errPrintln("EAssert Error: $msg"); throw Error(msg) }
}
fun tAssert(exp: Boolean, lazyMsg: () -> String = {""}) {
    if (!exp) { val msg = lazyMsg(); errPrintln("TAssert Error: $msg"); Thread.sleep(3000) }
}
class SolveThread : Runnable {
    override fun run() { solve() }
}
class Reader {
    private val br = BufferedReader(InputStreamReader(System.`in`))
    val readString: () -> String = { br.readLine() }
    val readInt: () -> Int = { br.readLine().toInt() }
    val readLong: () -> Long = { br.readLine().toLong() }
    val readIntArray: () -> IntArray = { br.readLine().split(' ').map { it.toInt() }.toIntArray() }
    val readLongArray: () -> LongArray = { br.readLine().split(' ').map { it.toLong() }.toLongArray() }
    val readListInt: () -> List<Int> = { br.readLine().split(' ').map { it.toInt() } }
    val readListLong: () -> List<Long> = { br.readLine().split(' ').map { it.toLong() } }
}


Measured memory_bytes: 106380