#include<stdio.h>
#define M 100000
#define SENTIMENTAL 2000000000

typedef struct{
  char suit;
  int value;
}Card;

Card L[M/2+2],R[M/2+2];

void merge(Card *,int,int,int,int);
void mergeSort(Card *,int,int,int);
int partition(Card *,int,int,int);
void quickSort(Card *,int,int,int);

int main() {

  int n,i,v;
  Card A[M],B[M];
  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;

}

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 = SENTIMENTAL;
  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);

  }

}

       

