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)

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

def merge(arr,left,mid,right)
    n1 = mid-left
    n2 = right-mid
    l = []
    r = []
    i = 0
    while i < n1
         l[i] =arr[left+i]
         i +=1
    end
    i = 0
    while i < n2
        r[i] = arr[mid+i]
        i +=1
    end
    l[n1] = "A",9999999999
    r[n2] = "A",9999999999
    i = 0
    j = 0
    k = left
    while k < right
        if l[i][1] <= r[j][1]
            arr[k] = l[i]
            i +=1
        else
            arr[k] = r[j]
            j +=1
        end
        k +=1
    end
end

def mergesort(arr,left,right)
    #leftは配列の先頭だから常に0。関数の中で関数を呼び出すからひたすら配列の要素が一つだけになるまでマージソートを繰り返す
    #要素の分解が１まできたことを表す。
    if left+1 < right
        mid =(left+right)/2
        #配列の左半分
        mergesort(arr,left,mid)
        #配列の右半分
        mergesort(arr,mid,right)
        merge(arr,left,mid,right)
    end
    return arr
end

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

n =gets.to_i
arr=[]
n.times do
    arr << gets.split(" ")
    arr.last[1] = arr.last[1].to_i
end
arr2 = arr.dup

arr  =mergesort(arr,0,n)
arr2 =quiksort(arr2,0,n-1)

if arr == arr2
    puts "Stable"
else
    puts "Not stable"
end

arr2.each do |obj,obj2|
    puts "#{obj} #{obj2}"
end