#include <stdio.h>
#define MAX 100000
#define SENTINEL 2000000000

typedef struct{
  char suit;
  int value;
} Card;

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

void merge(Card *A,int n,int left,int mid,int right){
  int i,j,k,n1,n2;
  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 = SENTINEL;
  R[n2].value = SENTINEL;
  i = 0;
  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(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(Card *A,int n,int p,int r){
  int i,j;
  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(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;
  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);
  return 0;
}