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)

/**
 * Created at 12:27 on 2019-08-29
 */

import java.io.*;
import java.util.*;
import java.util.function.Predicate;

public class Main {

  static FastScanner sc = new FastScanner();
  static Output out = new Output(System.out);

  static final int[] dx = {0, 1, 0, -1};
  static final int[] dy = {-1, 0, 1, 0};

  static final long MOD = (long) (1e9 + 7);
  static final long INF = Long.MAX_VALUE / 2;

  public static class Solver {
    public Solver() {

      int N = sc.nextInt();
      long H = sc.nextLong();

      Katana[] katana = new Katana[N];
      for (int i=0; i<N; i++) {
        katana[i] = new Katana(sc.nextInt(), sc.nextInt());
      }

      Arrays.sort(katana, (o1, o2) -> Compare.L(o2.b, o1.b));

      long[] sumB = new long[N+1];
      for (int i=1; i<=N; i++) {
        sumB[i] = sumB[i-1] + katana[i-1].b;
      }

      long ans = INF;
      for (int i=0; i<N; i++) {
        long a = katana[i].a;
        int index = BinarySearch.binarySearch(j -> katana[j].b >= a, 0, N, false);
        long h = H - sumB[index+1];
        ans = Math.min(ans, (index+1) + ceil(h, a) );
      }

      out.println(ans);

    }

    /*
     * n >= a/b なる最小の整数nを返す
     */
    public long ceil(long a, long b) {
      if (b < 0) {
        a *= -1;
        b *= -1;
      }

      if (a > 0) {
        //よくある切り上げのテクニック
        return (a+b-1)/b;
      } else {
        //絶対値の小さい方に丸められる(負なら正の方向)
        return a/b;
      }
    }

    public static class BinarySearch {

      /*
       * [l, r)の区間でchecker.test()を実行する
       * rightOK ... 右側OK左側NGならtrue, 右側NG左側OKならfalse
       */
      public static long binarySearchLong(Predicate<Long> checker, long l, long r, boolean rightOK) {
        long ng, ok;

        if (rightOK) {
          ok = r-1;
          ng = l;
          if (!checker.test(ok)) {
            return r;
          }
          if (checker.test(ng)) {
            return l;
          }
        } else {
          ok = l;
          ng = r-1;
          if (!checker.test(ok)) {
            return l-1;
          }
          if (checker.test(ng)) {
            return r-1;
          }
        }

        /* ok と ng のどちらが大きいかわからないことを考慮 */
        while (Math.abs(ok - ng) > 1) {
          long mid = (ok + ng) / 2;

          if (checker.test(mid)) ok = mid;
          else ng = mid;
        }

        return ok;
      }

      /*
       * [l, r)の区間でchecker.test()を実行する
       */
      public static int binarySearch(Predicate<Integer> checker, int l, int r, boolean rightOK) {

        int ng, ok;

        if (rightOK) {
          ok = r-1;
          ng = l;
          if (!checker.test(ok)) {
            return r;
          }
          if (checker.test(ng)) {
            return l;
          }
        } else {
          ok = l;
          ng = r-1;
          if (!checker.test(ok)) {
            return l-1;
          }
          if (checker.test(ng)) {
            return r-1;
          }
        }

        while (Math.abs(ok - ng) > 1) {
          int mid = (ok + ng) / 2;

          if (checker.test(mid)) ok = mid;
          else ng = mid;
        }

        return ok;
      }

      public static int lowerBound(long[] a, long v) {

        if (a[0] >= v) return 0;

        int l = 0, r = a.length;
        int mid = (r + l) / 2;

        while (r - l > 1) {

          if (a[mid] >= v) r = mid;
          else l = mid;

          mid = (r + l) / 2;
        }

        return r;

      }

      public static int upperBound(long[] a, long v) {

        if (a[0] > v) return 0;

        int l = 0, r = a.length;
        int mid = (r + l) / 2;

        while (r - l > 1) {

          if (a[mid] > v) r = mid;
          else l = mid;

          mid = (r + l) / 2;
        }

        return r;

      }

      public static int count(long[] a, long v) {
        int lower = lowerBound(a, v);
        int upper = upperBound(a, v);
        return upper - lower;
      }

    }

    class Katana {
      long a, b;
      Katana(long A, long B) {
        a = A;
        b = B;
      }
    }

    public static class Compare {
      public static int L(long l1, long l2) {
        if (l1 == l2) return 0;
        else if (l1 < l2) return -1;
        else return 1;
      }
    }

  }

  public static void main(String[] args) {
    new Solver();
    out.flush();
  }

  static class FastScanner {
    private final InputStream in = System.in;
    private final byte[] buffer = new byte[1024];
    private int ptr = 0;
    private int buflen = 0;

    private boolean hasNextByte() {
      if (ptr < buflen) {
        return true;
      } else {
        ptr = 0;
        try {
          buflen = in.read(buffer);
        } catch (IOException e) {
          e.printStackTrace();
        }
        if (buflen <= 0) {
          return false;
        }
      }
      return true;
    }

    private int readByte() {
      if (hasNextByte()) return buffer[ptr++];
      else return -1;
    }

    private static boolean isPrintableChar(int c) {
      return 33 <= c && c <= 126;
    }

    private void skipUnprintable() {
      while (hasNextByte() && !isPrintableChar(buffer[ptr])) ptr++;
    }

    public boolean hasNext() {
      skipUnprintable();
      return hasNextByte();
    }

    public String next() {
      if (!hasNext()) throw new NoSuchElementException();
      StringBuilder sb = new StringBuilder();
      int b = readByte();
      while (isPrintableChar(b)) {
        sb.appendCodePoint(b);
        b = readByte();
      }
      return sb.toString();
    }

    public long nextLong() {
      if (!hasNext()) throw new NoSuchElementException();
      long n = 0;
      boolean minus = false;
      int b = readByte();
      if (b == '-') {
        minus = true;
        b = readByte();
      }
      if (b < '0' || '9' < b) {
        throw new NumberFormatException();
      }
      while (true) {
        if ('0' <= b && b <= '9') {
          n *= 10;
          n += b - '0';
        } else if (b == -1 || !isPrintableChar(b)) {
          return minus ? -n : n;
        } else {
          throw new NumberFormatException();
        }
        b = readByte();
      }
    }

    public int nextInt() {
      return (int) nextLong();
    }

    public int[] nextIntArray(int N, boolean oneBased) {
      if (oneBased) {
        int[] array = new int[N + 1];
        for (int i = 1; i <= N; i++) {
          array[i] = sc.nextInt();
        }
        return array;
      } else {
        int[] array = new int[N];
        for (int i = 0; i < N; i++) {
          array[i] = sc.nextInt();
        }
        return array;
      }
    }

    public long[] nextLongArray(int N, boolean oneBased) {
      if (oneBased) {
        long[] array = new long[N + 1];
        for (int i = 1; i <= N; i++) {
          array[i] = sc.nextLong();
        }
        return array;
      } else {
        long[] array = new long[N];
        for (int i = 0; i < N; i++) {
          array[i] = sc.nextLong();
        }
        return array;
      }
    }
  }

  static class Output extends PrintWriter {

    public Output(PrintStream ps) {
      super(ps);
    }

    public void print(int[] a, String separator) {
      for (int i = 0; i < a.length; i++) {
        if (i == 0) print(a[i]);
        else print(separator + a[i]);
      }
      println();
    }

    public void print(long[] a, String separator) {
      for (int i = 0; i < a.length; i++) {
        if (i == 0) print(a[i]);
        else print(separator + a[i]);
      }
      println();
    }

    public void print(String[] a, String separator) {
      for (int i = 0; i < a.length; i++) {
        if (i == 0) print(a[i]);
        else print(separator + a[i]);
      }
      println();
    }

    public void print(ArrayList a, String separator) {
      for (int i = 0; i < a.size(); i++) {
        if (i == 0) print(a.get(i));
        else print(separator + a.get(i));
      }
      println();
    }
  }

}