#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];

void merge(struct Card A[], int n, int left, int mid, int right){
  int i, j, k;
  int n1 = mid - left;
  int 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 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(struct Card A[],int n,int p,int r){
  int i, j;
  struct Card w, x;
  x = A[r];
  i = p - 1;
  for ( j = p ; j < r ; j++ ){
    if ( A[j].value <= x.value ){
      i++;
      w = A[i];
      A[i] = A[j];
      A[j] = w;
    }
  }
  w = A[i+1];
  A[i+1] = A[r];
  A[r] = w;
  return i+1;
}

void quickSort(struct 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;
  struct Card A[MAX], B[MAX];
  char C[10];
  int stable = 1;
  scanf("%d",&n);

  for ( i = 0 ; i < n ; i++ ) {
    scanf("%s %d",C,&v);
    A[i].suit = B[i].suit = C[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);
  }
}
