#include<stdio.h>
#define LEN 100010
#define STABLE 1
#define NOTSTABLE 0

typedef struct{
  char c;
  int n;
}Card;

//quick
void quicksort(Card *, int, int);
int partion(Card *, int, int);

//marge
void merge(Card *, int, int, int);
void merge_sort(Card *, int, int);


int main()
{
  int n;
  Card A[LEN], M[LEN], card;
  int p, r;

  int flag=STABLE;

  int i, j, k;
  char c;

  //read
  scanf("%d", &n);
  scanf("%c", &c);
  for(i=0; i<n; i++)
    {
      scanf("%c %d", &A[i].c, &A[i].n);
      scanf("%c", &c);
      M[i]=A[i];
      //printf("%c %d\n", A[i].c, A[i].n);
    }


  //merge sort
  merge_sort(&M[0], 0, n);

  //quick sort
  p=0;
  r=n-1;
  quicksort(&A[0], p, r);

  //is this stable?
  for(i=0; i<n-1; i++)
    {
      if(A[i].c!=M[i].c)
	{
	  flag=NOTSTABLE;
	  break;
	}
    }

  //print
  if(flag==STABLE)printf("Stable\n");
  else printf("Not stable\n");
  for(i=0; i<n; i++)printf("%c %d\n", A[i].c, A[i].n);
  /*
  printf("\n");
  for(i=0; i<n; i++)printf("%c %d\n", M[i].c, M[i].n);
  */


  return 0;
}


//quicksort
void quicksort(Card *A, int p, int r)
{
  int q;
  if(p<r)
    {
      q = partion(A, p, r);
      quicksort(A, p, q-1);
      quicksort(A, q+1, r);
    }
}

//partion
int partion(Card *A, int p, int r)
{
  int x = A[r].n;
  int i = p-1;
  int j, n;
  Card k;

  for(j=p; j<=r-1; j++)
    {
      if(A[j].n<=x)
	{
	  i++;
	  k=A[i];
	  A[i]=A[j];
	  A[j]=k;
	}
    }

  k=A[i+1];
  A[i+1]=A[r];
  A[r]=k;
  return i+1;
}



//Merge method
void merge(Card *S, int left, int mid, int right)
{
  int i, j, k;
  int n1=mid-left;
  int n2=right-mid;
  Card L[LEN], R[LEN];

  for(i=0; i<n1; i++)L[i]=S[left+i];
  for(i=0; i<n2; i++)R[i]=S[mid+i];

  L[n1].n=1000000001;
  R[n2].n=1000000001;
  i=0;
  j=0;
  for(k=left; k<right; k++)
    {
      if(L[i].n<=R[j].n)
        {
          S[k]=L[i];
          i++;
        }
      else
        {
          S[k]=R[j];
          j++;
        }
    }
}

void merge_sort(Card *S, int left, int right)
{
  int mid;
  if(left+1<right)
    {
      mid=(left+right)/2;
      merge_sort(S, left, mid);
      merge_sort(S, mid, right);
      merge(S, left, mid, right);
    }
}