#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) {
  if(left+1 < right) {
    int 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++) {
    // マージソートとクイックソートの結果を比べる
    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;
}

