#include<stdio.h>
#define MAX 100005
#define BIG 1000000000

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 n1 = mid - left;
  int n2 = right - mid;
int i = 0,j = 0,k=0;
  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 = BIG;
  R[n2].value = BIG;
  i=0;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){
  if (left+1 < right) {
    int 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) {
  Card x = A[r],temp ;
  int i = p-1,j;
  for(j = p; j < r ;j++) {
    if(A[j].value <= x.value) {
      i++;
      temp = A[i];
      A[i] = A[j];
      A[j] = temp;
    }
  }
    temp = A[i+1];
    A[i+1] = A[r];
    A[r] = temp;
  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\n",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;
}