#include <stdio.h>
#include <stdlib.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);
	if (n < 1 || n > MAX)
		exit(1);

	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;
}
