#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 > 100000)
    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;
}
