#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 part(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 quick(struct 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;
  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,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;
}
      
  

