#include<stdio.h>

#define MAX 100000
#define SEN 2000000000

struct Card{
  char suit;
  int value;
};

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

void merge(struct Card *,int,int,int,int);
void mergeSort(struct Card *,int,int,int);
int partition(struct Card *,int,int,int);
void quickSort(struct Card *,int,int,int);

int main(){
  int n,i,a;
  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,&a);
    A[i].suit = B[i].suit = s[0];
    A[i].value = B[i].value = a;
  }

  mergeSort(A,n,0,n);
  quickSort(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;
}

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 = SEN;

  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 partition(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 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);
  }
}

