#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;
  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(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;
}