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: Wrong Answer)

class Card
  def initialize(mark, number)
    @mark = mark
    @number = number.to_i
  end

  def to_s
    "#{mark} #{number}"
  end

  attr_accessor :number, :mark
end

def partition(array, p, r)
  x = array[r].number
  i = p - 1
  p.upto(r - 1) do |index|
    if array[index].number <= x
      i += 1
      array[i], array[index] = array[index], array[i]
    end
  end
  array[r], array[i + 1] = array[i + 1], array[r]
  i + 1
end

def quick_sort(array, p, r)
  if p < r
    q = partition array, p, r
    quick_sort array, p, q - 1
    quick_sort array, q + 1, r
  end
  array
end

def merge(left_array, right_array)
  return_array = []
  left_index, right_index = 0, 0
  left_array << Card.new('', 10**9)
  right_array << Card.new('', 10**9)
  0.upto(left_array.length + right_array.length - 3) do
    if left_array[left_index].number < right_array[right_index].number
      return_array << left_array[left_index]
      left_index += 1
    else
      return_array << right_array[right_index]
      right_index += 1
    end
  end
  return_array
end

def merge_sort(target_array)
  right = target_array.length
  mid = target_array.length / 2
  left_array = target_array[0...mid]
  right_array = target_array[mid...right]
  return target_array if target_array.length == 1
  merge(merge_sort(left_array), merge_sort(right_array))
end

def stable?(merge, sorted)
  merge.each_with_index do |element, index|
    return false if element.mark != sorted[index].mark
  end
  true
end

n = gets.to_i
input_array = []
n.times do
  input = gets.split(' ')
  input_array << Card.new(input[0], input[1])
end

input_array2 = Marshal.load(Marshal.dump(input_array))
merge = merge_sort input_array
quick = quick_sort input_array2, 0, n - 1

if stable? merge, quick
  puts 'Stable'
else
  puts 'Not stable'
end

puts quick.map(&:to_s)