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)

Card = Struct.new(:suit, :value) do
  include Comparable

  def <=>(other)
    value <=> other.value
  end

  def to_s
    [suit, value].join(' ')
  end
end

def merge_sort(arr)
  return arr if arr.size <= 1

  mid = arr.size / 2

  arr1 = arr[0...mid]
  arr2 = arr[mid..-1]

  merge(merge_sort(arr1), merge_sort(arr2))
end

def merge(arr1, arr2)
  ret = []

  until arr1.empty? || arr2.empty?
    if arr1.first <= arr2.first
      ret << arr1.shift
    else
      ret << arr2.shift
    end
  end

  unless arr1.empty?
    ret.push(*arr1)
  end

  unless arr2.empty?
    ret.push(*arr2)
  end

  ret
end

def partition(arr, p, r)
  x = arr[r]
  i = p - 1
  p.upto(r - 1) do |j|
    if arr[j] <= x
      i += 1
      arr[i], arr[j] = arr[j], arr[i]
    end
  end
  arr[i + 1], arr[r] = arr[r], arr[i + 1]
  return i + 1
end

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

if $PROGRAM_NAME == __FILE__
  n = gets.to_i
  arr1 = []
  arr2 = []

  n.times do
    suit, value = gets.split
    card = Card.new(suit.to_sym, value.to_i)
    arr1 << card
    arr2 << card
  end

  quick_sort(arr1, 0, n - 1)
  arr2 = merge_sort(arr2)

  stable = true

  n.times do |i|
    if arr1[i].suit != arr2[i].suit
      stable = false
      break
    end
  end

  puts stable ? 'Stable' : 'Not stable'

  arr1.each do |card|
    puts card
  end
end