#include<bits/stdc++.h>

#define REP(i,n) for(int (i)=0;(i)<(n);++(i))
#define FOR(i,a,b) for(int (i)=(a);i<(b);++(i))
#define FOR_DOWN(i,a,b) for(int (i)=(a);i>=(b);--(i))
#define ALL(obj) (obj).begin(),(obj).end()
#define space <<" "<<
#define maxs(x,y) (x=max(x,y))
#define mins(x,y) (x=min(x,y))
#define FIX fixed<<setprecision(10)
using namespace std;

using ll = long long; using ull = unsigned long long;
using vb = vector<bool>; using vvb = vector<vb>;
using vi = vector<int>; using vvi = vector<vi>;
using vl = vector<ll>; using vvl = vector<vl>;
using pii = pair<int,int>; using pll = pair<ll,ll>;

const ll MOD = 1e9+7;

class Stack{
private:
char m[20000];
int tp;
public:
    Stack(){
    tp=0;
    }
    void push(char x){
        tp++;
        m[tp]=x;
    }
    char pop(){
        tp--;
        return m[tp+1];
    }
}; 
class Queue{
private:
pair<string,int> m[60000];
int head,tail;
public:
    Queue(){
        head=0;
        tail=0;
    }
    bool isEmpty(){
        return head==tail;
    }
    void enqueue(pair<string,int> x){
        m[tail]=x;
        if(tail +1 ==60000)tail=0;
        else tail++;
    }
    pair<string,int> deque(){
        pair<string,int> x=m[head];
        if(head+1==60000)head=0;
        else head++;
        return x;
    } 
};

struct Node{
    int key;
    Node* prev;
    Node* next;
};

class LinkedList{
public:
LinkedList(){
    dammy= new Node();
    dammy->key =0;
    dammy->prev= dammy;
    dammy->next= dammy;
}
~LinkedList(){
    Node* tmpNode =dammy->next;
    Node* nextNode;
    while(tmpNode != dammy){
        nextNode=tmpNode->next;
        delete tmpNode;
        tmpNode=nextNode;
    }
    delete dammy;
}
void insertNode(int x){
    Node* currentNode=dammy->next;
    dammy->next=new Node();
    dammy->next-> key =x;
    dammy->next->next=currentNode;
    dammy->next->prev=dammy;
    currentNode->prev = dammy->next;
}
    Node* find(int key){
    for(Node* i=dammy->next;i!=dammy;i=i->next){
      if(i->key==key)return i;
    }
    return dammy;
    }
    void deleteNode(int x){
    Node* currentNode = find(x);
    if(currentNode==dammy)return;
    currentNode->prev->next=currentNode->next;
    currentNode->next->prev=currentNode->prev;
    delete currentNode;
    }
    void deleteFirst(){
        Node* currentNode = dammy->next;
        dammy->next = dammy->next->next;
        dammy->next->prev = dammy;
        delete currentNode; 
    };
 
    void deleteLast(){
        Node* currentNode = dammy->prev;
        dammy->prev = dammy->prev->prev;
        dammy->prev->next = dammy;
        delete currentNode; 
    };

    void printList(){
    Node* currentNode = dammy->next;;
    int sp = 1;
    while(1){
    if ( currentNode == dammy ) break;
    if ( sp == 0)  cout<<" ";
    cout<<currentNode->key;
    currentNode = currentNode->next;
    sp = 0;
    }
    cout<<endl;
    }
    private:
    Node* dammy;
};
    int n;
void CountingSort(int* A,int* B,int k){
    int C[k+1];
    REP(i,k+1){
        C[i]=0;
    }
    REP(i,n){
        C[A[i+1]]++;
    }
    FOR(i,1,k+1){
        C[i]+=C[i-1];
    }
    for(int i=n;i>=1;i--){
        B[C[A[i]]]=A[i];
        C[A[i]]--;
    }
}

struct tramp{
    char mark;
    int number;
    int order;
};

void sw(tramp *a,tramp* b){
    tramp temp = *a;
    *a=*b;
    *b=temp;
}
int partition(tramp* A,int p, int r){
    int x= A[r].number;
    int i=p-1;
    for(int j=p;j<r;j++){
        if(A[j].number<=x){
            i=i+1;
            sw(&A[i],&A[j]);
        }
    }
    sw(&A[i+1],&A[r]);
    return i+1;
}
void quick(tramp*A,int p,int r){
    if(p<r){
        int q=partition(A,p,r);
        quick(A,p,q-1);
        quick(A,q+1,r);
    }
}

int main(){
    int n;
    bool stability=true;
    cin>>n;
    tramp A[n]; 
    for(int i=0; i<n;i++){
        cin>>A[i].mark;
        cin>>A[i].number;
        A[i].order=i;
    }
    quick(A,0,n-1);
    for(int i=0;i<n-1&&stability;i++){
        for(int j=i+1;j<n;j++){
            if(A[i].number==A[j].number&&A[i].order>A[j].order){
                stability=false;
                break;
            }
        }
    }
    cout<<(stability? "Stable":"Not stable")<<endl; 
    for(int i=0;i<n;i++){
        cout<<A[i].mark<<" "<<A[i].number<<endl;
    }
}



Measured memory_bytes: 4196