#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];

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++;
      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(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);
  }
}

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;
  }

  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;
}

