#include<stdio.h>
#define MAX 100000
#define SENTINEL 2000000000
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(i=0;i<n;i++)
	{
		l[i]=A[left+i];
	}
	for(i=0;i<n;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 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);
	}
}
int main()
{
	int n,i,v;
	struct card A[MAX],B[MAX];
	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(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;
}