#include <stdio.h>
#define MAX 100000
#define SEN 2000000000

typedef struct{
  char suit;
  int value;
}Card;

Card L[MAX/2+2], R[MAX/2+2];

void merge(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=SEN;

  i=j=0;

  for(k=left;k<right;k++){
    if(L[i].value<=R[i].value){
      A[k]=L[i++];
    }else{
      A[k]=R[j++];
    }
  }
}

void mergesort(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 part(Card A[], int n, int p, int r){
  int i, j;
  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 quick(Card A[], int n, int p, int r){
  int q;
  if(p<r){
    q=part(A,n,p,r);
    quick(A,n,p,q-1);
    quick(A,n,q+1,r);
  }
}

int main(){
  int n, i, v;
  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);
  quick(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;
}