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 C (judge verdict: Accepted)

#include <stdio.h>
#include <stdlib.h>
#define INFTY 1000000001

typedef struct{ //構造体
		int value;
		char key;
} Card;

int partition(Card *A, int  p, int r){
	int i, j, x;
	Card temp;
	x = A[r].value;
	//printf("x:%d\n", x);
	i = p-1;
	for(j=p; j<r; j++){
		if(A[j].value<=x){
			i=i+1;
			//A[i] と A[j] を交換
			temp=A[i];
			A[i]=A[j];
			A[j]=temp;
		}
	}
	//A[i+1] と A[r] を交換
	temp=A[i+1];
	A[i+1]=A[r];
	A[r]=temp;
	
	return i+1;
}

void quicksort(Card *A, int  p, int r){
	int q;
	if(p<r){
		q = partition(A, p, r);
		quicksort(A, p, q-1);
		quicksort(A, q+1, r);
	}
}
void merge(Card *B, int left, int mid, int right) //merge で統治
{
	int n1, n2;
	Card *L, *R;
	L=malloc(sizeof(Card)*right);
	R=malloc(sizeof(Card)*right);
	int i, j, k;
	n1=mid-left;
	n2=right-mid;
	//L[0...n1], R[0...n2] を生成
	for(i=0; i<n1; i++) L[i]=B[left+i];
	for(i=0; i<n2; i++) R[i]=B[mid+i];
	L[n1].value=INFTY;
	R[n2].value=INFTY;
	i=0;
	j=0;
	for(k=left; k<right; k++){
		if(L[i].value<=R[j].value){
			B[k]=L[i];
			i=i+1;
		}
		else{
			B[k]=R[j];
			j=j+1;
		}
	}
	
	free(L);
	free(R);
}

void mergeSort(Card *B, int left, int right) //mergeSort で分割. 部分配列の要素数が 1 以下のときは何もせず終了
{
	//部分配列の中央の位置 mid
	//部分配列の前半部分は left から mid （ mid は含まない
	//後半部分は mid から right （ right は含まない）
	int mid;
	if(left+1<right){
		mid=(left+right)/2;
		mergeSort(B, left, mid);
		mergeSort(B, mid, right);
		merge(B, left, mid, right);
	}
}

int main(void){
	int i, n, no=0;
	Card *A, *B;
	scanf("%d", &n);
	A=malloc(sizeof(Card)*n);
	B=malloc(sizeof(Card)*n);
	for(i=0; i<n; i++){
		scanf(" %c %d", &A[i].key, &A[i].value);
		B[i]=A[i];
	}
	
	quicksort(A, 0, n-1);
	mergeSort(B, 0, n);
	for(i=0; i<n; i++){
		if(B[i].key!=A[i].key){
			no=1;
			break;
		}
	}
	if(no) printf("Not stable\n");
	else printf("Stable\n");
	for(i=0; i<n; i++) printf("%c %d\n", A[i].key, A[i].value);
	
	free(A);
	free(B);
	return 0;
}