#include <stdio.h>

#define N 100000

typedef struct{
  char mark; //絵柄
  int num; //数字
  int s; //安定かの確認するための変数
} Card;

void quickSort(Card *,int,int);
int partition(Card *,int,int);

int main(void){

  int i,n,p = 0,r,f = 0;
  char c;
  Card A[N];

  scanf("%d%c",&n,&c);
  r = n-1;

  for(i=0;i<n;i++){
    scanf("%c%d%c",&A[i].mark,&A[i].num,&c);
    A[i].s = i;
  }

  quickSort(A,p,r);

  for(i=0;i<r-1;i++){
    if(A[i].num == A[i + 1].num && A[i].s > A[i + 1].s){
      printf("Not stable\n");
      f = 1;
      break;
    }
  }

  if(f == 0){
    printf("Stable\n");
  }
  
  for(i=0;i<n;i++){
    printf("%c %d\n",A[i].mark,A[i].num);
  }
  return 0;
}


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 partition(Card *A,int p,int r){

  int i,j,x;
  Card temp;

  x = A[r].num;
  i = p-1;

  for(j=p;j<r;j++){
    if(A[j].num <= x){
      i = i+1;
      temp = A[i];
      A[i] = A[j];
      A[j] = temp;
    }
  }
  temp = A[i+1];
  A[i+1] = A[r];
  A[r] = temp;
  return i+1;
}