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 Java8 (OpenJDK 1.8.0) (judge verdict: Wrong Answer)

import java.io.BufferedReader;
import java.io.Closeable;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.ListIterator;
import java.util.Map.Entry;
import java.util.PriorityQueue;
import java.util.Scanner;
import java.util.StringTokenizer;
import java.util.TreeMap;
import java.util.TreeSet;
 
public class Main {
	
	public static class Katana implements Comparable<Katana> {
		long a, b;
		
		public Katana(long a, long b){
			this.a = a;
			this.b = b;
		}

		@Override
		public int compareTo(Katana o) {
			return -Long.compare(this.b, o.b);
		}
	}
	
	public static void main(String[] args) throws IOException {
		try (Scanner sc = new Scanner(System.in)) {
			final int N = sc.nextInt();
			final long H = sc.nextLong();
			
			Katana[] ks = new Katana[N];
			
			long[] bs= new long[N];
			
			for(int i = 0; i < N; i++){
				final long a = sc.nextLong();
				final long b = sc.nextLong();
				
				ks[i] = new Katana(a, b);
				bs[i] = b;
			}
			
			Arrays.sort(bs);
			long[] b_post_sum = new long[bs.length + 1];
			for(int i = 1; i < b_post_sum.length; i++){
				b_post_sum[i] += b_post_sum[i - 1];
				b_post_sum[i] += bs[i - 1];
			}
			//System.out.println(Arrays.toString(bs));
			//System.out.println(Arrays.toString(b_post_sum));
			
			long min = Long.MAX_VALUE;
			for(final Katana katana : ks){
				final long curr_a = katana.a;
				
				int range_lower = -1, range_upper = N - 1;
				while(range_lower + 1 < range_upper){
					final int middle = (range_lower + range_upper) / 2;
					//System.out.println("> " + bs[middle] + " " + middle);
					
					if(bs[middle] < curr_a){
						range_lower = middle;
					}else{
						range_upper = middle;
					}
				}
				//System.out.println(range_lower + " " + range_upper);
				
				int p_sum_lower = range_lower, p_sum_upper = N;
				while(p_sum_lower + 1 < p_sum_upper){
					final int middle = (p_sum_lower + p_sum_upper) / 2;
					
					final long sum = b_post_sum[middle] - b_post_sum[range_upper];
					if(sum < H){
						p_sum_lower = middle;
					}else{
						p_sum_upper = middle;
					}
				}
				//System.out.println(p_sum_lower + " " + p_sum_upper);
				
				final int full_b_use_time = p_sum_upper - range_upper;
				final long full_b_use_sum = b_post_sum[p_sum_upper] - b_post_sum[range_upper];
				//System.out.println(full_b_use_time + " " + full_b_use_sum + " " + curr_a);
				
				if(full_b_use_sum < H){
					final long full_a_use_time = ((H - full_b_use_sum) + (curr_a - 1)) / (curr_a);
					//System.out.println(full_b_use_time + full_a_use_time);
					min = Math.min(min, full_b_use_time + full_a_use_time);
				}else{
					min = Math.min(min, full_b_use_time);
				}
				
			}
			
			System.out.println(min);
		}
	}
 
	public static class Scanner implements Closeable {
		private BufferedReader br;
		private StringTokenizer tok;
 
		public Scanner(InputStream is) throws IOException {
			br = new BufferedReader(new InputStreamReader(is));
		}
 
		private void getLine() throws IOException {
			while (!hasNext()) {
				tok = new StringTokenizer(br.readLine());
			}
		}
 
		private boolean hasNext() {
			return tok != null && tok.hasMoreTokens();
		}
 
		public String next() throws IOException {
			getLine();
			return tok.nextToken();
		}
 
		public int nextInt() throws IOException {
			return Integer.parseInt(next());
		}
 
		public long nextLong() throws IOException {
			return Long.parseLong(next());
		}
 
		public double nextDouble() throws IOException {
			return Double.parseDouble(next());
		}
 
		public int[] nextIntArray(int n) throws IOException {
			final int[] ret = new int[n];
			for (int i = 0; i < n; i++) {
				ret[i] = this.nextInt();
			}
			return ret;
		}
 
		public long[] nextLongArray(int n) throws IOException {
			final long[] ret = new long[n];
			for (int i = 0; i < n; i++) {
				ret[i] = this.nextLong();
			}
			return ret;
		}
 
		public void close() throws IOException {
			br.close();
		}
	}
}