// Slower C++ solution:
#include<iostream>

#include<stdio.h>

#define max 100000

#define sen 2000000000

using namespace std;



struct card{

	char suit;

	int value;

};

struct card l[max/2+2],r[max/2+2];



void merge(struct card a[],int n,int left,int mid,int right)

{

	int i,j,k;

	int n1=mid-left;

	int n2=right-mid;

	for(int i=0;i<n1;i++) l[i]=a[left+i];

	for(int i=0;i<n2;i++) r[i]=a[mid+i];

	l[n1].value=r[n2].value=sen;

	i=j=0;

	for(k=left;k<right;k++)

	{

		if(l[i].value<=r[j].value){

			a[k]=l[i++];

		}

		else{

			a[k]=r[j++];

		}

	}

}



void mergesort(struct card a[],int n,int left,int right)

{

	int mid;

	if(left+1<right)

	{

		mid=(left+right)/2;

		mergesort(a,n,left,mid);

		mergesort(a,n,mid,right);

		merge(a,n,left,mid,right);

	}

}



int partition(struct card a[],int n,int p,int r)

{

	int i,j;

	struct card t,x;

	x=a[r];

	i=p-1;

	for(j=p;j<r;j++)

	{

		if(a[j].value<=x.value)

		{

			i++;

			t=a[i];a[i]=a[j];a[j]=t;

		}

	}

	t=a[i+1];a[i+1]=a[r];a[r]=t;

	return i+1;

}



void quicksort(struct card a[],int n,int p,int r)

{

	int q;

	if(p<r)

	{

		q=partition(a,n,p,r);

		quicksort(a,n,p,q-1);

		quicksort(a,n,q+1,r);

	}

}



struct card a[max],b[max];

int main()

{

	int n,i,v;

	char s[10];

	int stable=1;

	

	scanf("%d",&n);

	

	for(i=0;i<n;i++)

	{

		scanf("%s %d",s,&v);

		a[i].suit=b[i].suit=s[0];

		a[i].value=b[i].value=v;

	}

	

	mergesort(a,n,0,n);

	quicksort(b,n,0,n-1);

	

	for(int i=0;i<n;i++)

	{

		if(a[i].suit!=b[i].suit) stable=0;

	}

	if(stable==1) printf("Stable\n");

	else printf("Not stable\n");

	for(i=0;i<n;i++)

	{

		printf("%c %d\n",b[i].suit,b[i].value);

	}

	return 0;

}

// Faster C++ solution for the same problem (measured speedup: 4.2487773637178545x):
#include<stdio.h>

#define MAX 100000

#define SENTINEL 2000000000

struct C

{

	char suit;

	int value;

};

struct C L[MAX/2+2],R[MAX/2+2];

void merge(struct C A[],int n,int left,int mid,int right)

{

	int i,j,k;

	int n1=mid-left;

	int n2=right-mid;

	for(i=0;i<n1;i++)L[i]=A[left+i];

	for(i=0;i<n2;i++)R[i]=A[mid+i];

	L[n1].value=R[n2].value=SENTINEL;

	i=j=0;

	for(k=left;k<right;k++)

	{

		if(L[i].value<=R[j].value)

		A[k]=L[i++];

		else 

		A[k]=R[j++];

	}

}

void mergeSort(struct C A[],int n,int left,int right)

{

     int mid;

	if(left+1<right)

	{

		mid=(left+right)/2;

		mergeSort(A,n,left,mid);

		mergeSort(A,n,mid,right);

		merge(A,n,left,mid,right);

	}

}

int partition(struct C A[],int n,int p,int r)

{

	int i,j;

    struct C t,x;

    x=A[r];

    i=p-1;

    for(j=p;j<r;j++)

    {

    	if(A[j].value<=x.value)

        {

        	i++;

        	t=A[i];A[i]=A[j];A[j]=t;

        }

	}

	t=A[i+1];A[i+1]=A[r];A[r]=t;

	return i+1;

}

void quickSort(struct C A[],int n,int p,int r)

{

	int q;

	if(p<r)

	{

		q=partition(A,n,p,r);

		quickSort(A,n,p,q-1);

		quickSort(A,n,q+1,r);

	}

}

int main()

{

	int i,n,v;

	struct C A[MAX],B[MAX];

	char S[10];

	int stable=1;

	scanf("%d",&n);

	for(i=0;i<n;i++)

	{

		scanf("%s %d",S,&v);

		B[i].suit=S[0];

		A[i].suit=B[i].suit;

		B[i].value=v;

		A[i].value=B[i].value;

	}

	mergeSort(A,n,0,n);

	quickSort(B,n,0,n-1);

	for(i=0;i<n;i++)

	{

		if(A[i].suit!=B[i].suit)stable=0;

	}

	if(stable==1)printf("Stable\n");

	else printf("Not stable\n");

    for(i=0;i<n;i++)

    {

    	printf("%c %d\n",B[i].suit,B[i].value);

    }

	return 0;

}