#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,x;
  struct Card X[MAX],Y[MAX];
  char S[10];
  int stable=1;

  scanf("%d",&n);

  for(i =0;i<n;i++){
    scanf("%s %d",S,&x);
    X[i].suit=Y[i].suit=S[0];
    X[i].value=Y[i].value=x;
  }

  mergeSort(X,n,0,n);
  quickSort(Y,n,0,n-1);

  for(i=0;i<n;i++){
    if(X[i].suit!=Y[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",Y[i].suit,Y[i].value);
  }

  return 0;
}

