#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, i, v;
  struct Card A[N], B[N];
  char S[10];
  int 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 l, int mid, int r){
   
  int i, j, k, n1, n2;
   
  n1 = mid - l;
  n2 = r - mid;
   
  for(i=0;i<n1;i++){
    L[i] = A[l + 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 = l; k < r; 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 l, int r){
   
  int mid;
   
  if (l+1 < r){
    mid = (l + r)/2;
    mergeSort(A, l, mid);
    mergeSort(A, mid, r);
    merge(A, left, mid, r);
  }
}
 
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-1; 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);
  }
}