#include <stdio.h>

#define MAX 100000
#define SENTINEL 2000000000
 
struct Card{
  char suit;
  int value;
};
 
struct Card L[MAX/2+2], R[MAX/2+2];


int partition(struct Card A[],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 merge(struct Card A[],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 = R[n2].value = SENTINEL;

  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 left,int right){
  int mid;
  if(left + 1 < right){
    mid = (left + right) / 2;
    mergeSort(A, left, mid);
    mergeSort(A, mid, right);
    merge(A,left,mid,right);
  }
}
 


 
void quickSort(struct Card A[],int p,int r){
  int q;
  if(p < r){
    q = partition(A,p,r);
    quickSort(A,p,q-1);
    quickSort(A,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, 0, n);
  quickSort(B, 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;
}


