#include<stdio.h>
#define MAX 100000
#define SE 2000000000

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

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

void merge(Card A[], int left, int mid, int right){
  int i, j, k, n1, n2;
  
  n1 = mid - left;
  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 = SE;
  i = j = 0;
  for( k = left ; k < right ; k++ ){
    if( L[i].value <= R[j].value ){
      A[k] = L[i];
      i = i +1;
    }
    else {
      A[k] = R[j];
      j = j + 1;
    }
  }

}

void mergeSort(Card A[], int left, int right){
  int mid;
  if( left + 1 < right ){
    mid = ( left + right ) / 2;
    mergeSort(A, left, mid);
    mergeSort(A, mid, right);
    merge(A, left, mid, right);
  }
}

int partition(Card A[], int p, int r){
  int i, j;
  Card x, t;
  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 p, int r){
  int q;
  if( p < r ){
    q = partition(A, p, r);
    quickSort(A, p, q-1);
    quickSort(A, 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, 0, n);
  quickSort(B, 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;
}

