#include<stdio.h>
#define MAX 100000
#define inf 1000000000

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

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

void merge(Card A[], int n, 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 = inf;
  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(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(Card A[], int n, int p, int r) {
  int i,j;
  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(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,stable = 1;
  Card A[MAX],B[MAX];
  char S[10];
  
  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;
}

