#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 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 = SENTINEL;
	int i = 0 , j = 0;
	for( int 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)
{
	if(left + 1 < right)
	{
		int 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)
{
	struct Card x = A[r];
	struct Card t;
	int i = p-1;
	int j;
	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;
}
