Problem:
Quick Sort

Let's arrange a deck of cards. Your task is to sort totally n cards. A card consists of a part of a suit (S, H, C or D) and an number. Write a program which sorts such cards based on the following pseudocode:

Partition(A, p, r)
1 x = A[r]
2 i = p-1
3 for j = p to r-1
4 do if A[j] <= x
5 then i = i+1
6 exchange A[i] and A[j]
7 exchange A[i+1] and A[r]
8 return i+1

Quicksort(A, p, r)
1 if p < r
2 then q = Partition(A, p, r)
3 run Quicksort(A, p, q-1)
4 run Quicksort(A, q+1, r)

Here, A is an array which represents a deck of cards and comparison operations are performed based on the numbers.

Your program should also report the stability of the output for the given input (instance). Here, 'stability of the output' means that: cards with the same value appear in the output in the same order as they do in the input (instance).

Input

The first line contains an integer n, the number of cards.

n cards are given in the following lines. Each card is given in a line and represented by a pair of a character and an integer separated by a single space.

Output

In the first line, print the stability ("Stable" or "Not stable") of this output.

In the following lines, print the arranged cards in the same manner of that of the input.

Constraints

1 ≤ n ≤ 100,000

1 ≤ the number of a card ≤ 109

There are no identical card in the input

Sample Input 1

6
D 3
H 2
D 1
S 3
D 2
C 1

Sample Output 1

Not stable
D 1
C 1
D 2
H 2
D 3
S 3

Sample Input 2

2
S 1
H 1

Sample Output 2

Stable
S 1
H 1

Solution in Ruby (judge verdict: Accepted)

class Msort
  attr_reader :arr, :count

  def initialize(arr)
    @arr = arr
    @count = 0
  end

  def exec(l=0, r=arr.length-1)
    if l < r
      mid = (r - l) / 2 + l
      exec(l, mid)
      exec(mid+1, r)
      merge(l, mid, r)
    end
  end

  def merge(left, mid, right)
    l = @arr[left..mid]
    r = @arr[mid+1..right]
    tl = l.shift
    tr = r.shift
    result = []
    loop do
      break if [tl, tr].all?(&:nil?)
      @count += 1
      if tl.nil?
        result << tr
        tr = r.shift
        next
      end
      if tr.nil?
        result << tl
        tl = l.shift
        next
      end
      if tl.number <= tr.number
        result << tl
        tl = l.shift
      else
        result << tr
        tr = r.shift
      end
    end
    (left..right).each.with_index(0) do |i, idx|
      @arr[i] = result[idx]
    end
  end

  def out
    arr.map do |c|
      "#{c.type} #{c.number}"
    end
  end
end

class Qsort
  attr_reader :arr

  def initialize(arr)
    @arr = arr
  end

  def exec(l=0, r=arr.length-1)
    if l < r
      q = partition(l, r)
      exec(l, q-1)
      exec(q+1, r)
    end
  end

  def partition(l, r)
    q = @arr[r].number
    i = l - 1
    (l..r-1).each do |j|
      if @arr[j].number <= q
        i += 1
        @arr[i], @arr[j] = @arr[j], @arr[i]
      end
    end
    @arr[i+1], @arr[r] = @arr[r], @arr[i+1]
    i+1
  end

  def out
    arr.map do |c|
      "#{c.type} #{c.number}"
    end
  end
end

class Card
  attr_reader :number, :type
  def initialize(number, type)
    @number = number
    @type = type
  end
end

n = gets.to_i
arr = []
n.times do
  t, n = gets.split
  arr << Card.new(n.to_i, t)
end
q = Qsort.new(arr.dup)
m = Msort.new(arr.dup)
q.exec
m.exec
qresult = q.out
mresult = m.out
puts qresult.join(' ') == mresult.join(' ') ? 'Stable' : 'Not stable'
qresult.each(&method(:puts))