#include<stdio.h>
#define MAX 100000
#define INFTY 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 n1,n2,j,k,i;
 
  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=INFTY;
  R[n2].value=INFTY;
  i=0;
  j=0;

  for(k=left;k<right;k++){
    if(L[i].value<=R[j].value){
      A[k]=L[i];
      i=i+1;
    }
    else{
      A[k]=R[j];
      j=j+1;
    }
  }
}

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 num, x;

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

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);
  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);
  }
}

