#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;
     }
    
