Problem:
Score : 400 points

Problem Statement

You are going out for a walk, when you suddenly encounter a monster. Fortunately, you have N katana (swords), Katana 1, Katana 2, …, Katana N, and can perform the following two kinds of attacks in any order:

Wield one of the katana you have. When you wield Katana i (1 ≤ i ≤ N), the monster receives a_i points of damage. The same katana can be wielded any number of times.

Throw one of the katana you have. When you throw Katana i (1 ≤ i ≤ N) at the monster, it receives b_i points of damage, and you lose the katana. That is, you can no longer wield or throw that katana.

The monster will vanish when the total damage it has received is H points or more. At least how many attacks do you need in order to vanish it in total?

Constraints

1 ≤ N ≤ 10^5

1 ≤ H ≤ 10^9

1 ≤ a_i ≤ b_i ≤ 10^9

All input values are integers.

Input

Input is given from Standard Input in the following format:

N H
a_1 b_1
:
a_N b_N

Output

Print the minimum total number of attacks required to vanish the monster.

Sample Input 1

1 10
3 5

Sample Output 1

3

You have one katana. Wielding it deals 3 points of damage, and throwing it deals 5 points of damage. By wielding it twice and then throwing it, you will deal 3 + 3 + 5 = 11 points of damage in a total of three attacks, vanishing the monster.

Sample Input 2

2 10
3 5
2 6

Sample Output 2

2

In addition to the katana above, you also have another katana. Wielding it deals 2 points of damage, and throwing it deals 6 points of damage. By throwing both katana, you will deal 5 + 6 = 11 points of damage in two attacks, vanishing the monster.

Sample Input 3

4 1000000000
1 1
1 10000000
1 30000000
1 99999999

Sample Output 3

860000004

Sample Input 4

5 500
35 44
28 83
46 62
31 79
40 43

Sample Output 4

9

Solution in Kotlin (1.0.0) (judge verdict: Accepted)

import java.io.*
import java.lang.*
import java.math.*
import java.util.*

// Constant
val sc = FastScanner()
val pw = PrintWriter(System.out)
const val MOD = 1000000007L
const val INF = 9223372036854775807L

// Main
fun main(args: Array<String>) {
    solve()
    pw.flush()
}


fun solve() {
    val n = nextLong()
    val h = nextLong()
    val katana = longAry2(n, 2)
    var maxslush = 0L
    var maxidx = 0L
    for (i in 0 until n) {
        katana[i][0] = nextLong()
        katana[i][1] = nextLong()
        if(katana[i][0] > maxslush) {
            maxslush = katana[i][0]
            maxidx = i
        }
    }
    katana.sortByDescending { it[1] }

    var throwcount = 0L
    var res = h
    var throwsum = 0L
    for (i in 0 until n) {
        if(katana[i][1] < maxslush) break
        throwsum += katana[i][1]
        throwcount++
        if(throwsum >= res) {
            println(throwcount)
            return
        }
    }

    res -= throwsum
    println(throwcount + (res + maxslush - 1) / maxslush)


}




// Rule
operator fun String.get(index: Long): Char {
    if (index !in 0L..Int.MAX_VALUE) throw IllegalArgumentException()
    return this[index.toInt()]
}
operator fun CharArray.get(index: Long): Char {
    if (index !in 0L..Int.MAX_VALUE) throw IllegalArgumentException()
    return this[index.toInt()]
}
operator fun CharArray.set(index: Long, value: Char) {
    if (index !in 0L..Int.MAX_VALUE) throw IllegalArgumentException()
    this[index.toInt()] = value
}
operator fun IntArray.get(index: Long): Int {
    if (index !in 0L..Int.MAX_VALUE) throw IllegalArgumentException()
    return this[index.toInt()]
}
operator fun IntArray.set(index: Long, value: Int) {
    if (index !in 0L..Int.MAX_VALUE) throw IllegalArgumentException()
    this[index.toInt()] = value
}
operator fun LongArray.get(index: Long): Long {
    if (index !in 0L..Int.MAX_VALUE) throw IllegalArgumentException()
    return this[index.toInt()]
}
operator fun LongArray.set(index: Long, value: Long) {
    if (index !in 0L..Int.MAX_VALUE) throw IllegalArgumentException()
    this[index.toInt()] = value
}
operator fun DoubleArray.get(index: Long): Double {
    if (index !in 0L..Int.MAX_VALUE) throw IllegalArgumentException()
    return this[index.toInt()]
}
operator fun DoubleArray.set(index: Long, value: Double) {
    if (index !in 0L..Int.MAX_VALUE) throw IllegalArgumentException()
    this[index.toInt()] = value
}
operator fun <T> Array<T>.get(index: Long): T {
    if (index !in 0L..Int.MAX_VALUE) throw IllegalArgumentException()
    return this[index.toInt()]
}
operator fun <T> Array<T>.set(index: Long, value: T) {
    if (index !in 0L..Int.MAX_VALUE) throw IllegalArgumentException()
    this[index.toInt()] = value
}
operator fun <T> MutableList<T>.get(index: Long): T {
    if (index !in 0L..Int.MAX_VALUE) throw IllegalArgumentException()
    return this[index.toInt()]
}
operator fun <T> MutableList<T>.set(index: Long, value: T) {
    if (index !in 0L..Int.MAX_VALUE) throw IllegalArgumentException()
    this[index.toInt()] = value
}

val LongArray.siz: Long
    get() = size.toLong()
val <T> Array<T>.siz: Long
    get() = size.toLong()
val <T> MutableList<T>.siz: Long
    get() = size.toLong()
val <T> MutableSet<T>.siz: Long
    get() = size.toLong()
val String.len: Long
    get() = length.toLong()

// Output
fun println(v: String) {
    pw.println(v)
}
fun print(v: String) {
    pw.print(v)
}

// Input
fun next() = sc.next()
fun nextLong() = sc.nextLong()
fun nextDouble() = next().toDouble()
fun nextAry(n: Long): Array<String> {
    val ary = ary(n)
    for (i in 0 until n) ary[i] = next()
    return ary
}
fun nextLongAry(n: Long): LongArray {
    val ary = longAry(n)
    for (i in 0 until n) ary[i] = nextLong()
    return ary
}
fun nextDoubleAry(n: Long): DoubleArray {
    val ary = doubleAry(n)
    for (i in 0 until n) ary[i] = nextDouble()
    return ary
}

// Statement
fun ary(n: Long, init: String = "") = Array(n.toInt()) { init }
fun longAry(n: Long, init: Long = 0L) = LongArray(n.toInt()) { init }
fun doubleAry(n: Long, init: Double = 0.0) = DoubleArray(n.toInt()) { init }
fun boolAry(n: Long, init: Boolean = false) = Array(n.toInt()) { init }
fun ary2(n: Long, m: Long, init: String = "") = Array(n.toInt()) { ary(m, init) }
fun longAry2(n: Long, m: Long, init: Long = 0) = Array(n.toInt()) { longAry(m, init) }
fun doubleAry2(n: Long, m: Long, init: Double = 0.0) = Array(n.toInt()) { doubleAry(m, init) }
fun boolAry2(n: Long, m: Long, init: Boolean = false) = Array(n.toInt()) { boolAry(m, init) }
fun ary3(n: Long, m: Long, k: Long, init: String = "") = Array(n.toInt()) { ary2(m, k, init) }
fun longAry3(n: Long, m: Long, k: Long, init: Long = 0L) = Array(n.toInt()) { longAry2(m, k, init) }
fun doubleAry3(n: Long, m: Long, k: Long, init: Double = 0.0) = Array(n.toInt()) { doubleAry2(m, k, init) }
fun boolAry3(n: Long, m: Long, k: Long, init: Boolean = false) = Array(n.toInt()) { boolAry2(m, k, init) }
fun list() = mutableListOf<String>()
fun longList() = mutableListOf<Long>()
fun doubleList() = mutableListOf<Double>()
fun strSet() = mutableSetOf<String>()
fun longSet() = mutableSetOf<Long>()
fun doubleSet() = mutableSetOf<Double>()
fun <E, V> map() = mutableMapOf<E, V>()

// Monoid
val addFunc = {a: Long, b: Long -> a + b}
val mulFunc = {a: Long, b: Long -> a * b}
val maxFunc = {a: Long, b: Long -> max(a, b)}
val minFunc = {a: Long, b: Long -> min(a, b)}
val gcdFunc = {a: Long, b: Long -> gcd(a, b)}
val lcmFunc = {a: Long, b: Long -> lcm(a, b)}
val xorFunc = {a: Long, b: Long -> a xor b}
fun calc(a: Long, b: Long, op: (Long, Long) -> Long) = op(a, b)

// Extension
fun LongArray.lowerBound(n: Long): Long {
    var ok = this.size.toLong()
    var ng = -1L
    while (abs(ok - ng) > 1) {
        val mid = (ok + ng) / 2
        if (this[mid] >= n) ok = mid
        else ng = mid
    }
    return ok
}
fun DoubleArray.lowerBound(n: Double): Long {
    var ok = this.size.toLong()
    var ng = -1L
    while (abs(ok - ng) > 1) {
        val mid = (ok + ng) / 2
        if (this[mid] >= n) ok = mid
        else ng = mid
    }
    return ok
}
fun MutableList<Long>.longLowerBound(n: Long): Long {
    var ok = this.size.toLong()
    var ng = -1L
    while (abs(ok - ng) > 1) {
        val mid = (ok + ng) / 2
        if (this[mid] >= n) ok = mid
        else ng = mid
    }
    return ok
}
fun MutableList<Double>.doubleLowerBound(n: Double): Long {
    var ok = this.size.toLong()
    var ng = -1L
    while (abs(ok - ng) > 1) {
        val mid = (ok + ng) / 2
        if (this[mid] >= n) ok = mid
        else ng = mid
    }
    return ok
}
fun LongArray.cumsum(op: (Long, Long) -> Long): LongArray {
    val s = longAry(this.size + 1L)
    s[1] = this[0]
    for (i in 1 until this.size) s[i + 1] = calc(s[i], this[i], op)
    return s
}
fun MutableMap<String, Int>.counting(n: Long) {
    repeat(n.toInt()) {
        val a = next()
        if (this.containsKey(a)) this[a] = this[a]!! + 1
        else this[a] = 1
    }
}
fun MutableMap<Long, Int>.longCounting(n: Long) {
    repeat(n.toInt()) {
        val a = nextLong()
        if (this.containsKey(a)) this[a] = this[a]!! + 1
        else this[a] = 1
    }
}

// Mathematics
fun abs(n: Long): Long = Math.abs(n)
fun abs(n: Double): Double = Math.abs(n)
fun max(vararg values: Long) = if (values.isEmpty()) -INF else values.max()!!
fun min(vararg values: Long) = if (values.isEmpty()) INF else values.min()!!
tailrec fun gcd(a: Long, b: Long): Long = if (b == 0L) a else if (a % b == 0L) b else gcd(b, (a % b))
fun lcm(a: Long, b: Long): Long = a / gcd(a, b) * b
fun erathos(n: Long): LongArray {
    val res = LongArray(n.toInt() + 1) { it.toLong() }
    for (i in 2..n) {
        if(i * i > n) break
        for (j in i * i..n step i) {
            if(res[j] == j) res[j] = i
        }
    }
    res[0] = -1L
    res[1] = -1L
    return res
}
fun modAdd(a: Long, b: Long) = if(a + b >= MOD) a + b - MOD else a + b
fun modpow(a: Long, n: Long, p: Long = MOD): Long {
    var res = 1L
    var ar = a
    var nr = n
    while (nr > 0) {
        if ((nr and 1) == 1L) res = res * ar % p
        ar = ar * ar % p
        nr = nr shr 1
    }
    return res
}
fun modinv(a: Long, p: Long = MOD): Long = modpow(a, p - 2, p)
fun ncr(n: Long, r: Long): Long {
    var a = 1L
    var b = 1L
    for (i in 1..r) {
        a = a * (n + 1 - i) % MOD
        b = b * i % MOD
    }
    return modinv(b, MOD) * a % MOD
}

class Combination(private val max: Long) {
    private val fac = longAry(max)
    private val finv = longAry(max)
    private val inv = longAry(max)
    private val p = MOD
    fun init() {
        fac[0] = 1
        fac[1] = 1
        finv[0] = 1
        finv[1] = 1
        inv[1] = 1
        for (i in 2 until max) {
            fac[i] = fac[i - 1] * i % p
            inv[i] = p - inv[p % i] * (p / i) % p;
            finv[i] = finv[i - 1] * inv[i] % p
        }
    }

    fun com(n: Long, r: Long): Long = if (n < r || (n < 0 || r < 0)) 0L else fac[n] * (finv[r] * finv[n - r] % p) % p
}

class Permutation(private val n: Long, private var searched: Long = 0L, private var nextIndex: Long = 0L) {
    private val size = fact(n)
    private val permList = longAry2(size, n)

    private tailrec fun fact(n: Long, ans: Long = 1L): Long {
        return if (n == 0L) ans
        else fact(n - 1, ans * n)
    }

    fun init() {
        create(0, longAry(n), boolAry(n))
    }

    private fun create(num: Long, list: LongArray, flag: Array<Boolean>) {
        if (num == n) {
            permList[searched] = list.copyOf()
            searched++
        }
        for (i in 0 until n) {
            if (flag[i]) continue
            list[num] = i
            flag[i] = true
            create(num + 1, list, flag)
            flag[i] = false
        }
    }

    fun hasNext(): Boolean {
        return if (nextIndex < size) {
            true
        } else {
            nextIndex = 0
            false
        }
    }

    fun nextPerm(): LongArray = permList[nextIndex++]
}

// Graph
data class Node(val id: Long, var past: Long = -1, val edges: MutableList<Edge> = mutableListOf())
data class Edge(val from: Long, val to: Long, val cost: Long = 1L)

fun dfs(nodes: Array<Node>, now: Long, seen: Array<Boolean>) {
    seen[now] = true
    for (edge in nodes[now].edges) {
        if (seen[edge.to]) continue
        dfs(nodes, edge.to, seen)
    }
}

fun bfs(nodes: Array<Node>, start: Long): LongArray {
    val queue = ArrayDeque<Long>()
    queue.add(start)
    val dist = longAry(nodes.size.toLong(), -1L)
    dist[start] = 0L
    while (queue.isNotEmpty()) {
        val now = queue.poll()
        for (edge in nodes[now].edges) {
            if (dist[edge.to] != -1L) continue
            dist[edge.to] = dist[now] + 1
            queue.add(edge.to)
        }
    }
    return dist
}

fun dijkstra(nodes: Array<Node>, start: Long): LongArray {
    val queue = PriorityQueue(16) { e1: Edge, e2: Edge ->
        return@PriorityQueue when {
            e1.cost < e2.cost -> -1
            e2.cost > e1.cost -> 1
            else -> 0
        }
    }
    queue.add(Edge(start, start, 0L))
    val dist = longAry(nodes.size.toLong(), INF / 2)
    dist[start] = 0
    while (queue.isNotEmpty()) {
        val now = queue.poll()
        if (dist[now.to] < now.cost) continue;
        for (edge in nodes[now.to].edges) {
            if (dist[edge.to] <= dist[edge.from] + edge.cost) continue
            dist[edge.to] = dist[edge.from] + edge.cost
            queue.add(Edge(edge.from, edge.to, dist[edge.to]))
            nodes[edge.to].past = edge.from
        }
    }
    return dist
}

class GridGraph(
    private val h: Long,
    private val w: Long,
    val nodes: Array<Node> = Array((h * w).toInt()) { Node(it.toLong()) },
    private val edges: IntArray = IntArray((h * w).toInt()) { 0 }
) {
    private val up = 1
    private val right = 2
    private val down = 4
    private val left = 8
    private val queue: ArrayDeque<Long> = ArrayDeque()
    private val startPos = longList()

    private fun pos(y: Long, x: Long) = y * w + x
    fun canUp(v: Long) = (edges[v] and 1) == 1
    fun canRight(v: Long) = ((edges[v] shr 1) and 1) == 1
    fun canDown(v: Long) = ((edges[v] shr 2) and 1) == 1
    fun canLeft(v: Long) = ((edges[v] shr 3) and 1) == 1

    fun init(s: Array<String>, check: Char = '.', road: Char = '.', start: Char = 'S') {
        for (i in 0 until h) {
            for (j in 0 until w) {
                if(s[i][j] != check && s[i][j] != start) continue
                if(i > 0 && s[i - 1][j] == road) edges[pos(i, j)] += up
                if(i < h - 1 && s[i + 1][j] == road) edges[pos(i, j)] += down
                if(j > 0 && s[i][j - 1] == road) edges[pos(i, j)] += left
                if(j < w - 1 && s[i][j + 1] == road) edges[pos(i, j)] += right
                if(s[i][j] == start) {
                    queue.add(pos(i, j))
                    startPos.add(pos(i, j))
                }
            }
        }
    }
    fun addStart(y: Long, x: Long) {
        startPos.add(pos(y, x))
        queue.add(pos(y, x))
    }

    fun bfs(): LongArray {
        val dist = longAry(h * w, -1L)
        for (i in startPos) {
            dist[i] = 0L
        }
        while (queue.isNotEmpty()) {
            val v = queue.poll()
            if(canUp(v) && dist[v - w] == -1L) {
                queue.add(v - w)
                dist[v - w] = dist[v] + 1L
            }
            if(canDown(v) && dist[v + w] == -1L) {
                queue.add(v + w)
                dist[v + w] = dist[v] + 1L
            }
            if(canLeft(v) && dist[v - 1] == -1L) {
                queue.add(v - 1)
                dist[v - 1] = dist[v] + 1L
            }
            if(canRight(v) && dist[v + 1] == -1L) {
                queue.add(v + 1)
                dist[v + 1] = dist[v] + 1L
            }
        }
        return dist
    }

}

// Data Structure
class UnionFind(size: Long) {
    private val par = LongArray(size.toInt()) { it.toLong() }
    private val size = longAry(size, 1L)
    private val diffWeight = longAry(size, 0L)
    fun root(x: Long): Long {
        return if (par[x] == x) {
            x
        } else {
            val r = root(par[x])
            diffWeight[x] += diffWeight[par[x]]
            par[x] = r
            par[x]
        }
    }
    fun weight(x: Long): Long {
        root(x)
        return diffWeight[x]
    }
    fun diff(x: Long, y: Long) = abs(weight(y) - weight(x))

    fun same(x: Long, y: Long): Boolean = root(x) == root(y)
    fun unite(x: Long, y: Long, d: Long) {
        var w = d
        w += weight(x)
        w -= weight(y)
        var a = root(x)
        var b = root(y)
        if (a == b) return
        if (size[a] < size[b]) {
            var tmp = a
            a = b
            b = tmp
            w = -w
        }
        size[a] += size[b]
        par[b] = a
        diffWeight[b] = w
    }

    fun size(x: Long): Long = size[root(x)]
}

class SegmentTree(
    private val a: LongArray,
    private val op: (Long, Long) -> Long,
    private val def: Long = 0,
    private val size: Int = a.size,
    private val n: Int = Integer.highestOneBit(size) shl 1
) {
    private val nodes = longAry(2L * n - 1, def)

    fun init() {
        for (i in 0 until size) nodes[i + n - 1] = a[i]
        for (i in n - 2 downTo 0) nodes[i] = calc(nodes[2 * i + 1], nodes[2 * i + 2], op)
    }

    fun update(x: Long, value: Long) {
        var index = x + n - 1
        nodes[index] = value
        while (index > 0) {
            index = (index - 1) / 2
            nodes[index] = calc(nodes[2 * index + 1], nodes[2 * index + 2], op)
        }
    }

    fun get(a: Long, b: Long) = getSub(a, b, 0L, 0L, n.toLong())
    private fun getSub(a: Long, b: Long, k: Long, l: Long, r: Long): Long {
        return when {
            r <= a || b <= l -> def
            a <= l && r <= b -> nodes[k]
            else -> {
                val vl = getSub(a, b, k * 2 + 1, l, (l + r) / 2)
                val vr = getSub(a, b, k * 2 + 2, (l + r) / 2, r)
                calc(vl, vr, op)
            }
        }
    }

    fun joinToString(separator: String) = nodes.drop(n - 1).take(size).joinToString(separator)
}

// Scanner
class FastScanner {
    private val sin: InputStream = System.`in`
    private val buffer: ByteArray = ByteArray(1024) { 0 }
    private var ptr = 0
    private var buflen = 0

    private fun hasNextByte(): Boolean {
        return when {
            ptr < buflen -> true
            else -> {
                ptr = 0
                buflen = sin.read(buffer)
                buflen > 0
            }
        }
    }

    private fun readByte(): Int {
        return when {
            hasNextByte() -> buffer[ptr++].toInt()
            else -> -1
        }
    }

    private fun isPrintableChar(c: Int) = c in 33..126

    fun hasNext(): Boolean {
        while (hasNextByte() && !isPrintableChar(buffer[ptr].toInt())) ptr++
        return hasNextByte()
    }

    fun next(): String {
        if (!hasNext()) throw NoSuchElementException()
        val sb = StringBuilder()
        var b = readByte()
        while (isPrintableChar(b)) {
            sb.appendCodePoint(b)
            b = readByte()
        }
        return sb.toString()
    }

    fun nextLong(): Long {
        if (!hasNext()) throw NoSuchElementException()
        var n = 0L
        var minus = false
        var b = readByte()
        if (b.toChar() == '-') {
            minus = true
            b = readByte()
        }
        if (b.toChar() !in '0'..'9') throw NumberFormatException()
        while (true) {
            when {
                b.toChar() in '0'..'9' -> {
                    n *= 10
                    n += b.toChar() - '0'
                }
                b == -1 || !isPrintableChar(b) -> return if (minus) -n else n
                else -> throw NumberFormatException()
            }
            b = readByte()
        }
    }

//    "The world doesn't need you."
//
//    fun nextInt(): Int {
//        val nl = nextLong()
//        if (nl !in Int.MIN_VALUE..Int.MAX_VALUE) throw NumberFormatException()
//        return nl.toInt()
//    }
}