#include<stdio.h>
#define MAX 100000
#define N 2000000000

typedef struct Card{
  char suit;
  int value;
}Card;

Card L[MAX / 2 + 2], R[MAX / 2 + 2];

void merge(Card A[], int left, int mid, int right) {
  int i, j, k,n1,n2;

  n1 = mid - left;
  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 = N;
  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(Card A[], int left, int right) {
  int mid;
  if (left + 1 < right) {
    mid = (left + right) / 2;
    mergeSort(A, left, mid);
    mergeSort(A, mid, right);
    merge(A, left, mid, right);
  }
}

int partition(Card A[], int p, int r) {
  int i, j;
  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(Card A[], int p, int r) {
  int q;
  if (p < r) {
    q = partition(A, p, r);
    quickSort(A, p, q-1);
    quickSort(A, q+1, r);
  }
}

int main() {
  int n, i, v;
  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, 0, n);
  quickSort(B, 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;
}

