#include<stdio.h>
#define N 100000
#define INFTY 1000000000
 
struct Card{
   
  char suit;
  int value;
   
};
 
struct Card L[N], R[N];
 
void merge(struct Card *, int, int, int);
void mergeSort(struct Card *, int , int);
int partition(struct Card *, int, int);
void quickSort(struct Card *, int, int);
 
 
 
int main(){
   
  int n;
  int i;
  int v;
  struct Card A[N], B[N];
  char S[10];
  int stable;
 
  stable = 1;
   
  scanf("%d", &n);
 
  for ( i = 0; i < n; i++ ) {
     
    scanf("%s %d", S, &v);
     
    A[i].suit = S[0];
    B[i].suit = S[0];
    A[i].value = v;
    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;
}
 
void merge(struct Card A[], int left, int mid, int right){
   
  int i, j, k;
  int n1;
  int 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 = 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++;
    }
    else {
      A[k] = R[j];
      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);
  }
}
 
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 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);
     
  }
   
}