#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 left,int mid,int right){
  int i,j,k,n1=mid-left,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 left,int right){
  int mid;
  if(left+1 < right){
    mid = (left+right)/2;
    mergeSort(A,left,mid);
    mergeSort(A,mid,right);
    merge(A,left,mid,right);
  }
}
int partition(struct Card A[],int p,int r){
  int i,j;
  struct Card a,x;
  x =A[r];
  i = p-1;
  for(j=p;j<r;j++){
    if(A[j].value <= x.value){
      i++;
      a = A[i];
      A[i] = A[j];
      A[j] = a;
    }
  }
  a = A[i+1];
  A[i+1] = A[r];
  A[r] = a;
  return i+1;
}
void quickSort(struct Card A[],int p,int r){
  int q;
  if(p<r){
    q = partition(A,p,r);
    quickSort(A,p,q-1);
    quickSort(A,q+1,r);
  }
}
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,0,n);
  quickSort(B,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);
  }
}



