#include <stdio.h>
#define MAX 100000
#define SENTINEL 2000000000

typedef struct Card{
	char suit;
	int value;
} Card;

Card L[MAX / 2 + 2], R[MAX / 2 + 2];

void merge(Card A[], int n, int left, int mid, int right);
void mergeSort(Card A[], int n, int left, int right);
int partition(Card A[], int n, int p, int r);
void quickSort(Card A[], int n, int p, int r);

int main(){
	int n,i,v;
	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;
}

void merge(Card A[], int n, int left, int mid, int right){
	int n1 = mid - left;
	int n2 = right - mid;
	for(int i = 0; i < n1; i++) {L[i] = A[left + i];}
	for(int i = 0; i < n2; i++) {R[i] = A[mid + i];}
	L[n1].value = R[n2].value = SENTINEL;
	int i = 0, j = 0;
	for(int k = left; k < right; k++){
		if(L[i].value <= R[j].value){
			A[k] = L[i++];
		}
		else{
			A[k] = R[j++];
		}
	}
}

void mergeSort(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(Card A[], int n, int p, int r){
	int i,j;
	Card tmp, x;
	x = A[r];
	i = p-1;
	for(j = p; j < r; j++){
		if(A[j].value <= x.value){
			i++;
			tmp = A[i];
			A[i] = A[j];
			A[j] = tmp;
		}
	}
	tmp = A[i + 1];
	A[i + 1] = A[r];
	A[r] = tmp;
	return i+1;
}

void quickSort(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);
	}
}

