#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 = SENTINEL;
	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);
	mergesort(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;
}