#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 mer(struct Card A[],int n,int l,int m,int r){
  int i,j,k;
  int n1=m-l;
  int n2=r-m;
  for(i=0;i<n1;i++) L[i]=A[l+i];
  for(i=0;i<n2;i++) R[i]=A[m+i];
  L[n1].value=R[n2].value=SEN;
  i=j=0;
  for(k=l;k<r;k++){
    if(L[i].value<=R[j].value){
    A[k]=L[i++];
    }
    else{
      A[k]=R[j++];
    }
  }
}



void mS(struct Card A[],int n,int l,int r){
  int m;
  if(l+1<r){
    m=(l+r)/2;
    mS(A,n,l,m);
    mS(A,n,m,r);
    mer(A,n,l,m,r);
  }
}


int par(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 qS(struct Card A[],int n,int p,int r){
  int q;
  if(p<r){
    q=par(A,n,p,r);
    qS(A,n,p,q-1);
    qS(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;
  }

  mS(A,n,0,n);
  qS(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;
}

