#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,stable = 1;
  struct Card A[MAX],B[MAX];
  char S[10];
  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;
}

