#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++){
        // 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;
}

    


