#include<stdio.h>
#define Max 100000
#define INF 2000000000

struct Card{
  char suit;
  int value;
};

struct Card L[Max/2+2];
struct Card R[Max/2+2];

void merge(struct Card A[],int n,int l,int m,int r){
  int i,j,k;
  int n1 = m - l;
  int n2 = r - m;

  for(i=0 ; i<n1 ; i++) L[i] = A[l+i];
  for(i=0 ; i<n2 ; i++) R[i] = A[m+i];
  L[n1].value = R[n2].value = INF;
  i = j = 0;
  for(k=l ; k<r ; k++){
    if(L[i].value <= R[j].value) A[k] = L[i++];
    else A[k] = R[j++];
  }
}

void mergeSort(struct Card[],int n,int l,int r){
  int m;
  if(l+1 < r){
    m = (l+r)/2;
    mergeSort(A,n,l,m);
    mergeSort(A,n,m,r);
    merge(A,n,m,r);
  }
}

int partition(struct Card[],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[r] = 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];
  struct Card B[Max];
  char S[10];
  int st = 1;

  scanf("%d",&n);

  for(i=0 ; i<n ; i++){
    scanf("%s %d",S,&v);
    A[i].suit = S[0];
    A[i].value = v;
    B[i].suit = S[0];
    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) st=0;

  if(st == 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;
}