#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<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=SENTINEL;
	i=0;
	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(int 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 j;
	struct Card t,x;
	x=A[r];
	int 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(void)
{
	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;
}
