// Slower C++ solution:
#include<stdio.h>

#include<algorithm>

#include<iostream>

using namespace std;

struct pai

{

    char huase[1];

    int shuzi;

} x[100005],v[100005];

bool f(pai a,pai b)

{

    return a.shuzi<b.shuzi;

}

pai L[100000/2+2],R[100000/2+2];

int fg(pai a[],int p,int r)

{

    pai x=a[r];

    int j=p,i=p-1;

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

    {

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

        {

            i++;

          swap(a[i],a[j]);

      /*int t=a[i];

      a[i]=a[j];

      a[j]=t;*/

        }

    }

    swap(a[i+1],a[r]);

    return i+1;

    /*int t=a[i+1];

    a[i+1]=a[j];

    a[j]=t;*/

}

void guibing(pai a[],pai b[],pai c[],int left,int mid,int right)

{

    int n1=mid-left;

    int n2=right-mid;

    for(int i=0;i<n1;i++)

    {

        b[i]=a[left+i];

    }

    for(int i=0;i<n2;i++)

    {

        c[i]=a[mid+i];

    }

    b[n1].shuzi=c[n2].shuzi=1000000002;

    int i=0,j=0;

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

    {

        if(b[j].shuzi<=c[i].shuzi)

        {

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

        }

        else a[k]=c[i++];

    }



}

void guigingpai(pai a[],int left,int right)

{

    if(left+1<right)

    {

        int mid=(left+right)/2;

        guigingpai(a,left,mid);

        guigingpai(a,mid,right);

        guibing(a,L,R,left,mid,right);

    }

}

void qs(pai a[],int left,int right)

{

    if(left<right)

    {

        int q=fg(a,left,right);

        qs(a,left,q-1);

        qs(a,q+1,right);

    }

}

int main()

{

    int n;

    scanf("%d",&n);

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

    {

        //cin>>x[i].huase;

        scanf("%s",&x[i].huase);

        scanf("%d",&x[i].shuzi);

        v[i].shuzi=x[i].shuzi;

        v[i].huase[0]=x[i].huase[0];

    }

    guigingpai(v,0,n);

    //stable_sort(v,v+n,f);

    qs(x,0,n-1);

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

    {

        printf("%s %d\n",v[i].huase,v[i].shuzi);

    }*/

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

    {

        if(x[i].huase[0]!=v[i].huase[0])

        {

             printf("Not stable\n");

             break;

        }



        if(i==n-1)

        {

            printf("Stable\n");

        }

    }

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

    {

        printf("%s %d\n",x[i].huase,x[i].shuzi);

    }

    return 0;

}

// Faster C++ solution for the same problem (measured speedup: 4.2836529565669546x):
#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;

}