// Slower C++ solution:
// #include <cstdio>

#include <iostream>

#include <vector>

using namespace std;



struct Card

{

  char pic;

  int num;

};



int partition(Card a[], int p, int r)

{

  int x = a[r].num;

  int i = p - 1;

  for (int j = p; j < r; j++)

    if (a[j].num <= x)

    {

      i++;

      swap(a[i], a[j]);

    }

  swap(a[i + 1], a[r]);

  return i + 1;

}



void quickSort(Card a[], int p, int r)

{

  if (p < r)

  {

    int q = partition(a, p, r);

    quickSort(a, p, q - 1);

    quickSort(a, q + 1, r);

  }

}



void merge(Card a[], int left, int mid, int right)

{

  int n1 = mid - left;

  int n2 = right - mid;

  Card l[n1 + 1], r[n2 + 1];

  for (int i = 0; i < n1; i++)

    l[i] = a[left + i];

  for (int i = 0; i < n2; i++)

    r[i] = a[mid + i];

  l[n1] = {'J', 1000000001};

  r[n2] = {'J', 1000000001};



  int i = 0, j = 0;

  for (int k = left; k < right; k++)

    if (l[i].num <= r[j].num)

    {

      a[k] = l[i];

      i++;

    }

    else

    {

      a[k] = r[j];

      j++;

    }

}



void mergeSort(Card a[], int left, int right)

{

  if (left + 1 < right)

  {

    int mid = (left + right) / 2;

    mergeSort(a, left, mid);

    mergeSort(a, mid, right);

    merge(a, left, mid, right);

  }

}



int main()

{

  int n, x;

  char p;

  // scanf("%d", &n);

  cin >> n;



  Card a[n], ms[n];

  for (int i = 0; i < n; i++)

  {

    // scanf("%s%d", &p, &x);

    cin >> p >> x;

    a[i] = {p, x};

    ms[i] = {p, x};

  }



  quickSort(a, 0, n - 1);

  mergeSort(ms, 0, n);



  bool isStable = true;

  for (int i = 0; i < n; i++)

    if (a[i].num != ms[i].num || a[i].pic != ms[i].pic)

    {

      printf("Not stable\n");

      isStable = false;

      break;

    }



  if (isStable)

    printf("Stable\n");



  for (int i = 0; i < n; i++)

    printf("%c %d\n", a[i].pic, a[i].num);



  return 0;

}

// Faster C++ solution for the same problem (measured speedup: 5.121848315350887x):
#include <cstdio>

#include <cstring>

#include <vector>

using namespace std;



struct Card

{

  char pic;

  int num;

};



int partition(Card a[], int p, int r)

{

  int x = a[r].num;

  int i = p - 1;

  for (int j = p; j < r; j++)

    if (a[j].num <= x)

    {

      i++;

      swap(a[i], a[j]);

    }

  swap(a[i + 1], a[r]);

  return i + 1;

}



void quickSort(Card a[], int p, int r)

{

  if (p < r)

  {

    int q = partition(a, p, r);

    quickSort(a, p, q - 1);

    quickSort(a, q + 1, r);

  }

}



void merge(Card a[], int left, int mid, int right)

{

  int n1 = mid - left;

  int n2 = right - mid;

  Card l[n1 + 1], r[n2 + 1];

  for (int i = 0; i < n1; i++)

    l[i] = a[left + i];

  for (int i = 0; i < n2; i++)

    r[i] = a[mid + i];

  l[n1] = {'J', 1000000001};

  r[n2] = {'J', 1000000001};



  int i = 0, j = 0;

  for (int k = left; k < right; k++)

    if (l[i].num <= r[j].num)

    {

      a[k] = l[i];

      i++;

    }

    else

    {

      a[k] = r[j];

      j++;

    }

}



void mergeSort(Card a[], int left, int right)

{

  if (left + 1 < right)

  {

    int mid = (left + right) / 2;

    mergeSort(a, left, mid);

    mergeSort(a, mid, right);

    merge(a, left, mid, right);

  }

}



int main()

{

  int n, x;

  char p;

  scanf("%d\n", &n);



  Card a[n], ms[n];

  for (int i = 0; i < n; i++)

  {

    scanf("%c%d\n", &p, &x);

    a[i] = {p, x};

    ms[i] = {p, x};

  }



  quickSort(a, 0, n - 1);

  mergeSort(ms, 0, n);



  bool isStable = true;

  for (int i = 0; i < n; i++)

    if (a[i].num != ms[i].num || a[i].pic != ms[i].pic)

    {

      printf("Not stable\n");

      isStable = false;

      break;

    }



  if (isStable)

    printf("Stable\n");



  for (int i = 0; i < n; i++)

    printf("%c %d\n", a[i].pic, a[i].num);



  return 0;

}