#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;
}

