#include<stdio.h>
#define MAX 100000
#define NIL 200000000

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 = NIL;
	R[n2].value = NIL;
	i=0, 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 quick(struct Card A[],int n,int p,int r){
	int q;
	
	if(p<r){
		q = partition(A, n, p, r);
		quick(A, n, p, q-1);
		quick(A, n, q+1, r);
	}
}

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[j] = t;
	
	return i+1;
}


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 = S[0];
		B[i].suit = S[0];
		A[i].value = v;
		B[i].value = v;
	}
	mergeSort(A,n,0,n);
	quick(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;
}

