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