#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];

typedef struct Card card;

void irekae(card a[], int i,int j){

  struct Card t;

  t=a[i];
  a[i]=a[j];
  a[j]=t;

}

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++;
      irekae(A,i,j);
    }
    else continue;
  }

  irekae(A,i+1,r);
  
  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);
  }
  else return;
}

void print(int stable, int n,card B[]){

  int i;

  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);
  }

}

int main() {
  int n, i, v;
  struct 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, n, 0, n);

  quickSort(B, n, 0, n - 1);
  for (i = 0; i < n; i++ ) {
    if ( A[i].suit != B[i].suit ) stable = 0;
  }

  print(stable,n,B);
  
  return 0;

}

