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 JAVA (judge verdict: Wrong Answer)

import java.io.BufferedReader;
import java.io.InputStreamReader;

public class Main {

	public static void main(String[] args) throws Exception {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		int n  = Integer.parseInt(br.readLine());
		Card[] cards = new Card[n];
		for(int i = 0 ; i < n ; i++){
			cards[i] = new Card(br.readLine(),i);
		}
		quickSort(cards,0,n - 1);

		StringBuilder sb = new StringBuilder();
		boolean flag = true;
		for(int i = 0 ; i < n ; i ++){
			if(flag){
				flag = isStable(cards,i);
			}
			sb.append(cards[i].getStr());
			sb.append("\n");
		}

		if(flag){
			sb.insert(0, "Stable" + "\n");
		}else{
			sb.insert(0, "Not stable" + "\n");
		}

		System.out.print(sb.toString());
	}

	private static void quickSort(Card[] cards,int begin,int end){

		//????????\???????????§???????????´????????????
		if(end - begin < 2){
			return;
		}

		int q = partition(cards,begin,end);

		//??????
		quickSort(cards,begin,q - 1);
		//??????
		quickSort(cards,q + 1,end);
	}

	private static int partition(Card[] cards,int begin,int end){

		//???????????????
		int standardNum  = cards[end].getNum();
		Card tmpCard;
		//?????????????°????????????§???index
		int x = begin - 1;
		for(int i = begin ; i <  end ; i++){
			//?????????????°?????????´????????\?????????
			if(cards[i].getNum() <= standardNum){
				tmpCard = cards[i];
				cards[i] = cards[++x];
				cards[x] = tmpCard;
			}
		}

		//????????¨??????????????????????????¨????????????????????????????§??????????
		tmpCard = cards[end];
		cards[end] = cards[++x];
		cards[x] = tmpCard;
		return x;
	}

	private  static boolean isStable(Card[] cards,int i){
		if(i == 0){
			return true;
		}else if(cards[i].getNum() == cards[i - 1].getNum()
				  &&
				  cards[i].getFirstIndex() < cards[i - 1].getFirstIndex()
				  )
		{
			return false;
		}else{
			return true;
		}
	}
}

class Card{
	private String str;
	private int num;
	private int firstIndex;

	Card(String str,int firstIndex){
		this.str = str;
		this.num = Integer.parseInt(str.substring(2));
		this.firstIndex = firstIndex;
	}

	public String getStr() {
		return str;
	}
	public int getNum() {
		return num;
	}
	public int getFirstIndex() {
		return firstIndex;
	}

}