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)

//gcc -o program test.c
//./program
// http://judge.u-aizu.ac.jp/onlinejudge/review.jsp?rid=4609152#2
#include<stdio.h>
#define MAX 100000
#define SENTINEL 2000000000

struct Card{
    char suit;//記号
    int value;//数
};
struct Card L[MAX/2+2],R[MAX/2+2];//カード情報を書くのする箱を作る

void merge(struct Card Do_merge[],int left,int mid,int right){
    int i,j,k;
    int left2mid=mid-left;
    int right2mid=right-mid;
    for(i=0;i<left2mid;i++){
        L[i]=Do_merge[left+i];
    }
    for(i=0;i<right2mid;i++){
        R[i]=Do_merge[mid+i];
    }
    L[left2mid].value=R[right2mid].value=SENTINEL;
    i=j=0;
    for(k=left;k<right;k++){
        if(L[i].value<=R[j].value){
            Do_merge[k]=L[i++];
        }else{
            Do_merge[k]=R[j++];
        }
    }
}

void mergeSort(struct Card Do_merge[],int left ,int right){
    int mid;
    if(left+1<right){
        mid=(left+right)/2;
        mergeSort(Do_merge,left,mid);
        mergeSort(Do_merge,mid,right);
        merge(Do_merge,left,mid,right);
    }
}

int partition(struct Card Do_quick[],int p,int r){//配列の分離
    int i,j;
    struct Card t,x;
    x=Do_quick[r];
    i=p-1;
    for(j=p;j<r;j++){
        if(Do_quick[j].value<=x.value){
            i++;
            t=Do_quick[i];//値の交換
            Do_quick[i]=Do_quick[j];
            Do_quick[j]=t;
        }
    }
    t=Do_quick[i+1];//値の交換
    Do_quick[i+1]=Do_quick[r];
    Do_quick[r]=t;
    return i+1;
}

void quickSort(struct Card Do_quick[],int p,int r){
    int q;
    if(p<r){
        q=partition(Do_quick,p,r);
        quickSort(Do_quick,p,q-1);
        quickSort(Do_quick,q+1,r);
    }
}

int main(void){
    int card_num;//カードの枚数n
    int card_value;//カードの値v
    struct Card Do_merge[MAX],Do_quick[MAX];
    char Suit[10];//記号を入力させる。間違って複数の文字を書いても止めないために配列にしている？
    int stable=1;//安定か否かのbool型

    scanf("%d",&card_num);//カードの枚数入力
    for(int i=0;i<card_num;i++){//カード情報入力
        scanf("%s %d",Suit,&card_value);
        Do_merge[i].suit=Do_quick[i].suit=Suit[0];
        Do_merge[i].value=Do_quick[i].value=card_value;
    }

    mergeSort(Do_merge,0,card_num);
    quickSort(Do_quick,0,card_num-1);
    for(int i=0;i<card_num;i++){
        //マージソートとクイックソートの結果を比較して安定か否の判定
        if(Do_merge[i].suit!=Do_quick[i].suit){
            stable=0;
        }
    }
    if(stable==1){
        printf("Stable\n");
    }else{
        printf("Not stable\n");
    }
    for(int i=0;i<card_num;i++){
        printf("%c %d\n",Do_quick[i].suit,Do_quick[i].value);
    }
    return 0;
}