#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(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 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;
}

