#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;
}

