#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 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 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 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;
}

