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

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

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

void merge(Card*, int, int, int, int);
void mergeSort(Card*, int, int, int);
int partition(Card*, int, int, int);
void quickSort(Card*, int, int, int);

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, 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;
}

void merge(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(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(Card A[], int n, 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 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);
    }
}

